一、现在分词短语作时间状语有以下三种情况：
1．分词动作一发生,谓语动作紧跟着发生,这时用现在分词的一般式作时间状语,其逻辑主语为句中的主语.常用的动词,如：hear,see,arrive,return,get to,look,open,close,leave,turn around,walk等,表示一个极短暂动作.
此种情况可以换作on+动名词,表示相同的意思.译作"一（刚）……就……".
此种情况也可以换作是when引导的时间状语从句,该从句的动词多用一般过去时表示.如：
Hearing their teacher's voice,the pupils stopped talking at once.（= On hearing their teacher's voice… = When they heard their teacher's voice,the pupils…）一听到教师的声音,学生们立即停止讲话.
2．谓语动作发生在分词所表示的动作过程之中,则用when /while+现在分词的一般式,分词的逻辑主语为句中的主语.此种情况可以用in+动名词的一般式代替.
也可以换作when、while引导的时间状语从句,该从句的谓语动词用进行时态.如：
Don't be careless when /while having an exam.= Don't be careless in having an exam.= Don't be careless when / while you are having an exam.考试时不要粗心.
注：此结构中,不能用其他连接词替换when或while.
3．分词所表示的动作完成之后,谓语动作才发生,则要现在分词的完成式,即having done的形式.分词的逻辑主语应是句中的主语.
这种情况可以用after+动名词的一般式表示.
这种情况也可以用after /when引导的时间状语从句来替换,该从句的谓语动词用过去完成式.如：
Having finished his homework the boy was allowed to watch TV play.
After having finished his homework,the boy…
After /when he had finished his homework,the boy…