that的用法，要看它用于什么样的从句中：
定语从句：指代物或人，作主语时，不可省略；作宾语时，可省略。当先行词是人和物时，一般不省略。
名词性从句包括：主语从句，宾语从句，表语从句和同位语从句。在以上名词性从句中，只有在宾语从句中菜可以省略；其他情况下，都不可省略。
强调句型：It is ...that...中的也不能省略
扩展资料
在一般情况下，宾语从句中的that只起引导作用，在句中不做任何成分，没有实际意义，通常可以将其省略。例如，
I think (that)he’ll be all right in a few days.
Current trends indicate (that)transportation is becoming cleaner,faster and safer.
但是，that在引导宾语从句时并非在任何情况下都可以省略。在以下情况中，that不能省略。
（1）and 连接两个或两个以上的宾语从句时，第一个that可以省略也可以不省，但其它不能省略，以免产生误会：
Galileo’s observations show (that) Copernicus, another great astronomer, was right and that the earth moves around the sun, not the other way around.
(2) that引导的宾语从句放在except ,but 等介词后面的时候,that不能省略.
He is a good student except that he is a little careless.
(3) that 引导的宾语从句放在句首起强调作用的时候,that不能省略.
That he ever said such a thing I simply don’t believe.
(4) 主句谓语动词和that引导的宾语从句之间有插入的时候,that不能省略
Everyone could see , I believe , that Tom was really afraid .
(5) it 作形式宾语时,that 引导的宾语从句中的that不能省略.
We thought it strange that Xiao Wang did not come yesterday.
(6) 在对话中简短回答时,如果that引导的宾语从句独立出现,that不能省略.
---What did he say ?
---That he won the first prize in the game .
(7) 在可接双宾语动词后that引导的宾语从句作直接宾语的时候,that不能省略.
The foreign friend tells us that Chinese is one of the most difficult languages to learn .
(8) 在that引导的宾语从句之前或之后紧接着一个状语的时候,that不能省略.
He suddenly caught sight of the boy and realized at once that he had seen him before.
(9) 在直接引语中,that引导的宾语从句与主句隔开的时候,that不能省略,.
“I’m sorry to say,” he said ,“that you are not the suitable person for the work.”
1. 宾语从句前有插入语。如：
We hope, on the contrary, that he will stay at home with us. 恰恰相反，我们希望他和我们呆在家里。
2. 有间接宾语时。如：
He told me that he was leaving for Japan. 他告诉我他要去日本。
3. that在与之并列的另一个宾语从句之后。如：
He said (that) the book was very interesting and that(不省略) all the children like to read it.他说那本书很有趣，所有小孩都喜欢读。
4. 在“it(形式宾语)+补语”之后时。如：
I think it necessary that he should stay here. 我们认为他有必要留在这里。
5. that从句单独回答问题时。如：
—What did he hear? 他听说了什么事？
—That Kate had passed the exam. (他听说)凯特考试及格了。
6. 在except等介词后。如：
He has no special fault except that he smokes too much.他除了抽烟太多之外,没有什么特别的毛病。
7. 位于句首时。如：
That our team will win, I believe. 我相信我们队会赢。
8. 在较为正式或不常用的动词(如reply, object)后。如：
He replied that he disagreed. 他回答说他不同意。本回答被提问者采纳
that引导的宾语从句作介词宾语时不能省略。
and连接两个宾语从句,that宾语从句放在and的后面时,that不能省略。
从句位于句首时,that不可省略。
主句谓语动词与that从句之间有插入语,that不可省略。
如果是不在从句中无奈主语，可以省略。
爱剪辑-不能省略that的宾语从句