It is great fun playing with him分析
问题描述：
It is great fun playing with him分析
答
It是形式主语，playing with him是真正主语，句子其实就是Playing with him is great fun.
is是系动词，great是表语，之所以用playing是因为有短语fun in dong sth. in可以省略
答
与他一起玩很开心。it 是指代playing with him，这句话的主语是playing with him，主语后置，it 来替代。
答
It在句中作形式主语,真正的主语是动名词短语playing with him.这个句子也可以这样说,Playing with him is great fun.但英语中有时习惯用it做形式主语,这样句子显得不那么头重脚轻.例如,It's so nice to meet you.It'...