It is+adj+doing sth与It is+adj+to do sth有什么区别
It is+adj+to do sth和it+adj+to do sth 的区别：
1、 It is important to drink enough water every day.
it形式主语，没有意思的。to drink enough water every day，真正主语。意思是：每天喝足够的水很重要。,而谓语is important，使用了形式主语，而把真正主语放在后面，所以句型：It is+adj+to do sth的意思是：做某事怎么样。
2、 Doctors think it is important to drink enough water every day.
这时候It is important to drink enough water every day.
是宾语从句,作think的宾语.因为think 可以形成think+ 宾语+宾语补足语,所以此句可改成Doctors think it important to drink enough water every day。也就是少了be动词is，此时，it是形式宾语，important为宾语补足语to drink enough water every day为真正宾语。
拓展资料
It is+adj+doing sth
1、Germany should understand this because that is precisely what it is doing.
德国应理解这点，因为这正是该国正在做的事情。
2、How hard it is doing this.
这些事做起来行难。
3、Fortunately, it is doing so.
幸运的是，西方正在这么做。
4、With three built-in sensors, the iPhone knows more about what it is doing than I do.
使用三个内置感应器，iPhone知道我要干什么。
5、It is doing this with effortlessly simple products that are a pleasure to use.
它这样做的轻松愉快的是使用简单的产品这一点。
it+adj+to do sth
1、How difficult is it to do business with the company?
和那家公司做生意有多难？
2、You still need to test that the generated code actually does what you expect it to do, however.
然而，还需要测试所生成代码真的完成了您所期望的任务。
3、And how do you use it to do better work?
还有，如何利用它来达到更好的工作效果呢？
4、Would you choose this field if you had it to do over again?
如果再来一次，你还会选择这个行业吗？
5、In an OO system, a class shouldn't exist unless there's something for it to do; there must be responsibilities ( operations).
在OO系统中，类如果没有事情可做就不应该存在；必须有职责（操作）。
一般情况是：不定式和动名词都可以在句中作主语，但下面一些词的后面一般用doing，如hopeless,useless,no use,no good等等。大多还是用to do作主语。如：
It is no use crying spilt over milk (动名词）
It isn't easy to studyEnglish.(不定式)
至于你举的例子，我觉得你可以从不定式和动名词的基本含义去把握。一般而言，不定式表将来，表具体的行为，表主动等；而动名词多表现在，表经常性的行为，表主动等。
另外，有时是两种情况都可以的。比如：
Seeing is believing.(=To see is to believe.) 眼见为实。
这里你只要注意主语和表语保持形式上的一致就行，至于是用不定式还是动名词，则是两者兼可。
It is + no use,no good (fun,a great pleasure,a waste of time,a bore等名词）+doing sth.
t is no use crying.哭没有用。
It is no good objecting.反对也没有用。
It is a great fun playing football.打篮球很有趣。
It is a waste of time trying to explain.设法解释是浪费时间。
It is + useless (nice,good,interesting,expensive等形容词)+ doing sth.
It is useless speaking.光说没用。
It is nice seeing you again.真高兴又遇到了你。
It is good playing chess after supper.晚饭后弈棋挺好。
It is expensive running this car.开这种小车是浪费。
张老师教你如何使用句型It's+adj.+of sb.+to do sth.
前者多指一次性具体的行为，而后者多指经常性习惯性的动作。
