不是的。
to有两种情况,含有to的短语里面:
1.是固定搭配,既不能用其他的短语代替想表达的意思的:
look forward to(prep.)+doing something期待某事
set down to doing something开始着手某事
2.可以替代的:
want to do something=would like to do something
have to do something与need to do something意思相近.
to是介词情况的短语还是需要靠记忆。
追问及物动词后面加动词的话,都是doing形式,对吗?
追答不一定啊,你看look forward to,look是不及物的对吧,只能用look at something,但是它的这个短语中to是介词。