I’m looking forward to.和I look forward to.用的时候有什么区别?如题比如写信的最后说 I’m looking forward to hearing from you soon.和I look forward to hearing from you soon.

这看句子的时态吧...

I'm looking forward to是进行时态，用来表示我正在期待着...例如写信的结尾常常会有I'm looking forward to your reply（我正期待着你的回信）
I look forward to是一般现在时态，用来表示一种长期以来的习惯，如I look forward to had seen JAY someday.（我期待着有一天能够亲眼见到周杰伦）

两者其实区别不大,你如果一定要鸡蛋里挑骨头,则有这样的解释：
1、从语气上来说,-ing 形式比较personal 和friendly,和 look forward to...相比较少为正式,如果你要表示礼貌而有亲和力则用looking forward to...,look forward to在非常正式严谨的business场合比较适用.
2、国外英语论坛上native speaker给的解释二：
“The difference is how the speaker perceives their own words:
an action seen as a whole/accomplished (I look forward...) or continuing (I am looking...).
一个动作的结束（look forward to...）和一个动作的持续（looking forward to...）
Unless very self-aware or possibly an English teacher,an ordinary native speaker will be unable to explain their choice between the two and so the difference between a mental impression (I look forward) and a mental activity (I'm looking forward).In such cases,attempting to explain these subtleties to your students may prove counterproductive,unless of course they're advanced enough to handle it.It is my policy,that until then they're perfectly fine knowing there is no real difference there.”

I'm looking forward to 是强调[正在],因为用的是进行时.
I look forward to 强调的是[一直],因为用的是一般时.