impress 是及物动词，其中一个用法是接单宾语，然后跟介词短语 on sb. 

格式是： impress sth. on sb. 让某人知道/铭记某事。

宾语可以是sth. 也可以是 that 从句。由于太长而后移，这样介词短语 on sb. 提前，把 “动宾” 分隔开来。例如：

I impressed on him the importance of his work. 

（= I impressed the importance of his work on him. ）

我向他强调了他的工作的重要性。

Try to impress on her the tragic effect of her actions. 

让她铭记她的行为所带来的灾难性后果。

I want to impress on everyone that the bad times are over. 

我想让每个人都知道，糟糕的时代已经过去了。

His parents try to impress on him that it is very important to be honest.

他的父母尽力让他记住诚实是很重要的。

英语中，动词有这样的用法并不少见。例如，explain 也是如此。

explain sth. to sb.  = explain to sb. sth.

explain to sb. that 从句

例如：

I explained to him the importance of studying English.

（I explained the importance of studying English to him.）

I explained to him that I would not have to pay for my meal.