将来完成时用来表示在将来某一时间以前已经完成或一直持续的动作。经常与before+将来时间或by+将来时间连用，也可与before或by the time引导的现在时的从句连用。
如：We hope it will have stopped raining before we set off for the picnic. 我们希望在出发去野餐以前雨就已经停了。
I'll have done all the work by the time you are back this evening. 你们今晚回来的时候我就将做完所有的工作了。
①by(the time/the end of)+表示将来时间的短语和句子；
②before(the end of)+表示将来时间的词语或句子；
例如：By the year 2050, scientists probably will have discovered a cure for cancer.
By the time you arrive in London, we will have been staying in Europe for two weeks.
例如：You'll get to like the subject after you have studied it for some time.
I'll go and see the exhibition as soon as I have finished my work. 我一做完作业就去看展览。
例如：It's five o'clock, they will have arrived home by now. 已经五点钟了，他们现在应该已经到家了。
如：Mr Smith will return home on the first Sunday next month. 史密斯先生将于下月的第一个星期日回家。
如：Mr Smith will have returned home by next month. 到下个月史密斯先生将已回到家了。
1、They_____on the program for almost one week before I joined them, and now we_____it as no good results have come out so far.
A. had been working; are still working
B. had worked; were still working
C. have been working; have worked
D. have worked; are still working
解析：不难看出第一空的动作发生在I joined them以前，且持续了一个周，应该用过去完成进行时；and now说明下面的动作仍在进行之中，应该用现在进行时。故选A。
2、Father_____for London on business up on my arrival, so I didn't see him.
解析：由"I didn't see him"可知父亲在我回来以前已经离开，动作发生在过去某个动作以前，故选用过去完成时。
3、The policeman's attention was suddenly caught by a small box which_____placed under the Minister's car.
A. has been
B. had been
C. was being
D. would be