to 后面一定要跟 动词原形嘛？ 为什么我有时候看到句子里，to 后面接的是ing的词汇。

to 后面一定要跟 动词原形嘛？

不一定! 当to引导不定式时，后边的动词要用原形。

I need to work hard to learn English well.

My mother expects me to be number one in my class, and I find it hard to achieve the target.

为什么我有时候看到句子里，to 后面接的是ing的词汇?

英语里有几个以to 结尾的介词短语要求后面加动词+ing, 没道理,记住就可以了.

look forward to 加动词+ing.

I look forward to being alone in the house. 

我盼望着能自己一人待在这所房子里。

Come and bring your wife of other guest. Welook forward toseeing you. 

请您届时携带夫人或其他一位客人光临。我们期待着您的到来。

I must say Ilook forward tohearing him.

我得说我期望听他的报告。

I look forward tocoming to work every day.

我每天都迫不及待来上班。

object to 加动词+ing

I object to being jumped upon for trivial matter like this. 

我讨厌因这种小事而受人责备。

I must say I object to her gossiping.

我得说我很反对她说长道短。

Do you object to my closing the window?

我把窗子关上可以吗？

Would you object to my turning on the radio?

你会反对我开收音机吗?

I object to paying twice for the same thing.

我反对一件东西付两次款。