正确.
一、I 是整个句子的主语,think作谓语,it作形式宾语,important作宾语补足语,for us表对 象,to learn English well 是真正的宾语.
二、如果句子换做I think it is important for us to learn English well.
I是句子的主语,think作谓语,think之后是一个由that引导的宾语从句,其中that可以省略.it is important for us to learn English well.是一个宾语从句.在宾语从句中,it作主语,is是系动词,important作表语,for us 表对象,to learn English well是真正的主语.