1.be going to 表示近期、眼下就要發(fā)生的事情,will 表示的將來時(shí)間則較遠(yuǎn)一些,如：

　　He is going to write a letter tonight.

　　He will write a book one day.

　　2.be going to 表示根據(jù)主觀判斷將來肯定發(fā)生的事情,will表示客觀上將來勢必發(fā)生的事情.

　　He is seriously ill.He is going to die.

　　He will be twenty years old.

　　這里的be實(shí)際上也是省略了to的不定式to be（將是）.這里的will是助動詞,本身無意義,只起語法作用.

　　3.be going to 含有“計(jì)劃,準(zhǔn)備”的意思,而 will 則沒有這個(gè)意思,如：

　　She is going to lend us her book.

　　He will be here in half an hour.

　　4.在有條件從句的主句中,一般不用 be going to,而多用will,如：

　　If any beasts comes at you,I'll stay with you and help you.

　　這里的will是情態(tài)動詞,stay是to stay省略了to.