兩者其實(shí)區(qū)別不大,你如果一定要雞蛋里挑骨頭,則有這樣的解釋：
1、從語氣上來說,-ing 形式比較personal 和friendly,和 look forward to...相比較少為正式,如果你要表示禮貌而有親和力則用looking forward to...,look forward to在非常正式嚴(yán)謹(jǐn)?shù)腷usiness場(chǎng)合比較適用.
2、國(guó)外英語論壇上native speaker給的解釋二：
“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...).
一個(gè)動(dòng)作的結(jié)束（look forward to...）和一個(gè)動(dòng)作的持續(xù)（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.”