是him, 因为at是介词，后面要接宾格做宾语。

pron. 他（宾格）And I got to know him a little bit .我对他稍微有些了解。Think about him or her as a person .把他或她当成一个人来看待。It takes him two hours to get home .他要花两个小时才能到家。I 've known him for almost 22 years .我跟他认识快22年了。Another possibility : just wait him out .另外一种可能：等着他离开。

因为at是介词，后面要跟人称代词的的宾格形式him，形成介宾结构，例如：

1.I didn't dare look at him.我不敢看他。

2.He was watching her fixedly, willing her to look at him.他凝视着她，希望她也看他。

3.To look at him you'd never think he was nearly fifty.看他的外表，谁也想不到他年近五十了。

是him不是he.,因为at为介词，后接宾格him，中文意思是，看他。

When Spinks entered they all turned to look at him.当斯平克斯进来的时候，他们都转过来看着他。

Mari tilted her head back so that she could look at him.

玛丽把头向后仰了仰，以便能看着他。

是look at him

look是不及物动词，后面带不了宾语，但是它和介词at构成动介动词词组，at后面就可以带宾语了，表示看的对象、目标。至于look at后我为什么选him,是因为它后面要的是宾语，人称代词he是主格，作主语用的，不可作宾语，him是人称代词宾格，作宾语用的，所以选用look at him.