他已经离开北京四天了。英文怎么说？

He left beijing 4 days ago.

He has been away from Beijing for four days.

这两句是对的.
但是第一句用的是过去时 意思是 他四天前去的北京
第二句最好!
其他的句子是错误的,因为leave表示动作,是不延续性动词,所以句中不能与for+一段时间连用.
be away from是表示状态的,是延续性的,所以正确.

他已经离开北京四天了
He has been left Beijing for four days

He has been away from Beijing for four days.

用LEFT是不正确的,它不是延续动词.

He left Beijing four days ago. 或

He has been away from Beijing for four days.

he has been away of Beijing for 4 days.

He left beijing 4 days ago.