1、be going to表示近期、眼下就要发生的事情，will表示的将来时间则较远一些，如:He is going to write a letter tonight. He will write a book one day.
2、be going to表示根据主观判断将来绝对发生的事情，will表示客观上将来势必发生的事情。如：He is seriously ill. He is going to die. He will be twenty years old.
3、be going to含有“打算，准备”的意思，而will则没有这个意思，如：She is going to lend us her book. He will be here in half an hour.
4、在有条件从句的主句中，一般不用 be going to，而多用will。如：If any beast comes at you, I’ll stay with you and help you.
5、will可以表示主动为他人做某事或是给出一个承诺，可以翻译为“为”和“会”。 It is very cold. I will make you some hot coffee. If you take part in the election, I will support you.
