AbstractThere are many factors about individual differences that can influence effect of the second language learning, and the age is one of the most important factors. This has arisen more attention of both researchers and linguists. This paper will introduce some renowned theories at first; then will analyse the relationship between the factor--age, and the second language learning; and finally will illustrate with my own experience.IntroductionThere are many factors that can influence the two language acquisition, the age is one of the important factors. Studies on the age did not produce the same result, and even produced some contradictory results. Some scholars believe that children are the best of the second language learners, while some think adults are the best because of their hard work. And some believe that adolescents are the best learner. Owing to researchers have no consistent conclusion, we should first find out the similarities and differences of different ages, so at last find the best learning age to learn the second language. In the end, we could find appropriate solutions to make learning easier and more easily.BodyⅠ、relevant theory-----the critical period hypothesisThe critical period hypothesis states that there is a period when language acquisition takes place naturally and effortlessly. Penfiel and Roberts are the pioneer who created the critical period hypothesis. But they, two well-known neurosurgeons, argued that the optimum age for language acquisition falls within the first ten years of life. During this period the brain retains plasticity, but with the onset of puberty this plasticity begins to disappear. They suggested that this was the result of lateralization of the language function in the left hemisphere of the brain. That is, the neurological capacity for understanding and producing language, which initially involves both hemisphere of the brain, is slowly concentrated in the left hemisphere for most people. Before puberty, both hemispheres are involved in language comprehension and production. But with the onset of puberty (by the age of 12 or 13), lateralization of the language function in the left hemisphere of the brain occurs. Lateralization refers to the specialization of each of the hemisphere of the brain for different cognitive functions (each side of the brain performs specific functions). Neither of the hemispheres in adults completely duplicates the functions carried out by the other. There is evidence to support the critical period hypothesis from Lenneberg (1967)：1）Injuries of the right hemisphere caused more language problems in childrenthan in adults. 2) Children who underwent surgery of the left hemisphere, no speech disorders resulted, whereas with adults almost total language loss occurred. This suggested that the neurological basis of language in children and adults was different.Ⅱ Research status of the second language acquisitionOn the relationship between age and the two language acquisition, many theorists and applied linguists have done a lot of research, but there are still many disputes, especially on the critical period hypothesis. In 1960s, Lenneberg (1967) put forward the critical period hypothesis. He believes that from two to adolescence (10 ~ 12), the human brain is plastic, so language learning is easier. Lenneberg thinks children after 12 years old, accent has been fixed, so learning a language must spend more effort, and may not learn as well as the native language. However, Krashen believes that in the same situation in terms of time and target language and at the early stage of learning about vocabulary and syntax, older children could learn the second language faster than younger children. And Krashen thinks that adults can also learn a foreign language well, and if adult can use the same time to learn and use the second language, adult can learn faster than children, and older children can learn faster than younger children. Stern (1985) made a summary about the influence of age towards the second language learning. He believes that the critical period does not exist in the second language acquisition, andthe learners of all ages have their strengths and weaknesses. The smaller children are easier to make inflections intuitively in communicative situations, and older children and adults are more likely to use cognitive approaches to learning. That is to say people of any age can learn a second language. Ellis (1985) believe that adults initially has the advantage in the speed of acquisition, especially in terms of syntax; but if in the environment of formal language learning, only child learners could speak native language like a native resident; whether or not be able to achieve proficiency of the native speakers, children can reach the higher level than adults in terms of pronunciation and degree they could reach at proficiency.Ⅲ relationship between the factor---age and the second language learning1)children learnersAccuracy of pronunciation and oral language of the second language is related to the age of learners. Children learners usually speak more idiomatic and pure the second language than adults. And if after puberty learners began to learn a second language, it is not easy to speak the second language like a native speaker.Ann Fathman(1975) and Spolsky (1989), respectively, through the investigation and experiments showed similar findings: for phonetic system, the earlier learners begin to learn, the better effect is made. In 1990, Long found that: to start learning a second language before the ageof 6, speech does not exist foreign cavity in general; to start learning a second language from 6 to12 years old, some learners’speech will be with foreign accent and some one will be not; and after the age of 12, learners generally have a foreign accent.LuXiaoYong, the scholar of China, made an empirical study about the oral English level of his two graduate student classes. And he found that if children learn English from the age of four or five, most of them reached a relative high level in terms of the oral English ability and comprehensive capacity when they were at the stage of bachelor's degree and postgraduate. Conversely, if the students began to learn English from junior middle school, it is difficult to achieve such a high level. Thus, it is better to learn a second language from an earlier age.Ⅳ adolescent learnersWhere grammar and vocabulary are concerned, adolescent learners do better than either children or adults, when the length of exposure is held constant. This is because adolescent can ‘pick up’ language like a child, and they can supplement this process by conscious study.Ⅴ adult learnersFrom cognitive linguistics, little children could learn or think with a abstract mind like adults. Halliday（1973）pointed out，the young child responds not so much to what language is as to what it does. As a result that adult possesses abstract thinking, adult learners could not learnnaturally. But there are two advantages of adult. One is that if the time of study is the same the learning rate of adult is better than children. The other is that adult usually has a strong motivation to learn. Thus，adult learners should make full use of their advantages to learn.ConclusionAt present, many domestic and foreign places appear the phenomenon that some schools from primary school or even kindergarten opened English courses. We could not deny the advantages of critical period that one is more likely to hold pronunciation of foreign language speakers; the other is more likely to reach the ultimate level. However, from aspects of learning rate and grammar, the second language acquisition is not so better with a young age. This paper draws the following conclusions and suggestions.Ⅰstarting ageWe should learn a foreign language after the mother tongue acquisition. It is not wise to learn foreign languages at the cost of sacrificing time of native language acquisition. In the critical period for language acquisition we should ensure to complete the mother tongue acquisition otherwise children can not achieve a good result for two languages. The optimum starting age of second language learning is in 9 or 10 years old. In the 9 or 10 years old, mother tongue acquisition has basically completed, and students have certain development in the aspect of cognition, so they can learn both efficiently and own perfect oral language. This is because the age is still in a critical period of language learning, so the brain still has certain plasticity.Ⅱ implicationOwing to the optimum starting age of second language learning, adolescent learners should take advantages to study actively. Parents should pay more attention on this period. Adults should make use of the advantages of learning motivation and cognitive ability to make a better result. They could through various means make conscious induction and summary in learning process. But for adults, it is better to learn early. In addition, the pronunciation is not all things of a language so it is not necessary to demand their own pronunciation so purelyAnalysis influence of age on the second language acquisition姓名：王焕莲班级：2011级英本4班学号：11030144016。