不定式完成式在句中可以用作以下成分：
一、主语
To have made the same mistake twice was unforgivable. 两次犯同样的错误是不可原谅的。
To have told my secret would have given me away. 要是讲出了我的秘密就是把我自己出卖了。
有时在句首使用形式主语。如：
It’s nice to have finished work. 工作干完了，真惬意。
二、表语
He seems to have been hurt. 他似乎受伤了。
The house was to have been ready today. 这座房子本应该今天竣工。
I was to have seen him last Wednesday but he did not come. 我本来打算在上星期三和他见面的但是他没有来。
三、宾语
He pretended to have read the book. 他假装曾经读过那本书。
I hate to have quarreled with her. 我后悔和她吵架了(
www.yygrammar.com)。
They claimed to have shot down 22 planes. 他们声称打下了22架飞机。
四、定语
There is no need to have bought a new pair of shoes for me. 没有必要给我买一双新鞋。
She’s the only woman ever to have climbed Everest in winter. 她是唯一在冬天爬过埃佛勒斯峰的妇女。
五、状语
You’re far too clever to have done that. 你太聪明了不会这样做。
He was too young to have learned to say no to a woman. 他太年轻了，还没学会向女人说不。
六、宾补
I believed her to have done this on purpose. 我相信她是故意这样做的。
I consider him to have acted disgracefully. 我认为他的行为不光彩。
They supposed man to have descended from animals. 他们认为人是动物演变来的。
七、主补
He is rumoured to have escaped to Dublin. 谣传他已逃往都柏林。
He was known to have taken money from the Germans. 据传他拿过德国人的钱。
They are believed to have landed in America. 人们相信他们在美洲上了岸。
He is reported to have been chosen chairman of the trade union. 据说他当选了工会主席。