an amount of通常与不可数、无生命的名词连用.如：
She spent a very large amount of money yesterday.她昨天花了好大一笔钱.
a number of与可数、有生命或无生命的名词连用.如：
The president has made a large number of mistakes.总统已犯了许多错误.
an amount of一般是指某个物体的的多少,一般用an large amount of等.the amount of一般是某个物体的具体的数量,后面一般加名词.
a number of与an amount of的意思差不多,但一般后面加群体性的名词,如:people.the number of也和the amount of差不多,也是后面一般加群体性名词