She is as tall as me.其中as 是介词后面如果加人称一定要加人称的宾格,如me,him,them等等.
She is as tall as I am.其中I am是一个省略句,原句应该为she is as tall as I am tall.但为了避免重复就把tall省去而已.
两个句子的结构不一样,自己慢慢斟酌一下.