as后一定加宾语吗？

好像你在问as后面必须跟成分吗?是的，它后面必须跟成分，无论它是用作介词还是连词。
1.作介词用时，后面可以跟名词也可以跟其他的结构:
He is considered as the best student in our class.
He works as a teacher in the school.
He is regarded as clever.
2.做连词用：He is as tall as Tom.
Tall as he is ,he can't reach the picture.

不！比如：
The child sang as sweetly as a nightingale.

很少见过+宾格的
大部分都主格的