状语从句在复合句中作状语，位置灵活。
状语从句可分为时间状语从句，目的状语从句，条件状语从句，让步状语从句，地点状语从句，原因状语从句，方式状语从句，结果状语从句。
（一）时间状语从句1.when, as, whilea.when表时间，从句既可以用延续性动词，又可以用瞬间动词。
Eg: When I get there I will call you.如果when引导的时状的主语与主句的主语相同，而从句的谓语又是be动词时，那么从句中的主语与be 可省。
Eg：When （you are）in trouble, you can ask her for help.如果when引导的时状的主语与主句的主语相同时，往往可以用“when+分词”的形式代替该状从。
Eg：When I came into the room(When coming into the room), I found the light was off.b.while表时间，从句需用延续性动词，或者主句的动作发生在从句的动作进行过程中。
主句的谓语动词通常是非延续性动词。
Eg: He came in while I was reading a book.I met her while I was in school.c. as表时间，与when相似，但侧重强调主从句动作同在时间点或同时间段进行。
同时可表示主句的动作随着从句的动作的变化而变化。
Eg: He jumps as he sings.As the wind rose, the noise increased.2.before(在……之前)与after（在……之后）Eg：See me before you leave.I saw them after I arrived.3. till与until肯定形式表示的意思是"做某事直至某时"。
否定形式表达的意思是"直至某时才做某事"。
Eg: Wait till/untill I call you.等着直到我叫你。
She didn't arrive till/until 6 o'clock..她直到6点才到但是置于句首时只可用untill.Until you told me, I had heard nothing of what happened. 直到你告诉我以前，出了什么事我一点也不知道。
否定形式有另外两种表达方式：(1)Not until …在句首，主句用倒装。
Man did not know what heat was until the early years of the 19th century.=Not until the early years of the 19th century did man know what heat was.(2)It is not until…that…He will not go to bed until his mother comes home.=It is not until his mother comes home that he will go to bed.4. as soon as/the moment/the instant/the second/the minute/immediately和hardly/scarcely…when, no sooner…thana. as soon as/the moment/the instant/the second/the minute/immediately 表示主句和从句的动作同时发生。
译为“一……就”Eg：As soon as she heard the news, she began crying.b. hardly/scarcely…when, no sooner…than都可以表示"一……就……"的意思，但主句谓语动词一般要用过去完成时，从句谓语动词要用一般过去时。
Eg：I had hardly / scarcely got home when it began to rain.I had no sooner got home than it began to rain.注意：如果hardly, scarcely 或no sooner置于句首，句子必须用倒装结构：Hardly / Scarcely had I got home when it began to rain.No sooner had I got home than it began to rain。
1. We called the First - Aid Center_______ the traffic accident happened.A. immediatelyB. shortlyC.quicklyD. hurriedly2. The roof fell _____he had time to dash into the room to save his baby.A. beforeB. asC. afterD. until3. A good storyteller must be able to hold his listeners’ curiosity he reaches the end of the story.A whenB whenever C.after D.until4. I had just started back for the house to change my clothes _______ I heard the voices.A. asB. forC. whileD.when5. ______ the day went on, the weather got worse.１A. WithB. SinceC. WhileD. As(二)目的状语从句1. (so) that/in order that（so）that/in order that表示“为了，以便”，引导的目的状语从句要用虚拟语气。
Eg: He shouted at the top of his voice so that/in order that he might be heard.如果表示“为了，以便”的目的状语从句的主语与主句的主语相同，可用in order to或so as to替代。
Eg：I came early so as to/in order to catch the first train.3.lest, for fear that, in caselest, for fear that, in case表示“以免，以防”。
其中lest, for fear that要用(should)+动词原形的虚拟语气；in case 后的从句可用虚拟语气，也可用陈述语气。
Eg：I will not make a noise lest/ for fear that I (should) disturb you.Take your umbrella in case it rains.Ex.1. He whispered to his wife_______ he might wake up the sleeping baby.A. so thatB. on condition thatC. for fear thatD. so long as2. Roses need special care they can live through winter.A. because B so that C even if D as3. Leave your key with a neighbour you lock yourself out oneday.A ever sinceB even ifC soon afterD in case4. Take your umbrella with you ____________ it rains.A. ifB. as ifC. in caseD. as long as5. I hurried _____ I wouldn’t be late for class.A. sinceB. so thatC. as ifD. unless(三)条件状语从句1. if: “如果”(如为真实条件句用陈述语气、如为非真实条件句用虚拟语气)Eg: If it snows tomorrow, the flight will be canceled.If I were a bird, I would fly.2. in case, on condition that, provinding, provided (that), supposing, supposed (that) :“假如，在……条件下”Eg: The mother promises to the son to buy him a toy airplane on condition that he passes his English test. Suppose (that) he does not come, what shall we do?3. unless:“除非”（=if not）Eg: We can’t get there on time unless we book the ear liest flight= We cannot get there on time if we don’t book the earliest flight.4.as/so long as:“只要”Eg: We will succeed as long as we keep on trying.Ex1. --What are you going to do this afternoon?--I’ll probably go for a walk later on ___ it stays fine.A. as far asB. so long asC. even ifD. as if2. We will have a picnic in the park this Sunday it rains.A sinceB ifC unlessD until3. You will pass the exam you work hard.A unlessB even ifC as ifD if（四）让步状语从句1. “虽然，即使，尽管”a. although/ though/ even though/ even ifalthough/ though 语气较弱（尽管），even though/ even if（即使）语气较强。