1.be going to 表示按计划或安排要做的事情,而will表示临时打算或决定.例如:
I'm going to play football after school.放学后我要去踢足球.
Please lie down,and I'll examine you.请躺下,我要给你做下检查(通常医生说的话).
2.be going to表示有迹象要做某事或发生某事,而will则没有,它只表示纯粹的将来.例如:
There is too much cloud in the sky.It seems that It's going to rain.空中云很多,似乎要下雨了.
He will be 18 next year.明年他就18岁了.
3.will还表示意愿,而be going to 则没有这种用法.例如:
I'll do my best .我会尽力的.
希望对你有所帮助.有不懂的继续问我.