Question

定语从句有没有只能用who引导不能用that的情况

Answer 1

以下是定语从句中用who不用that的情况:

1) 当先行词为人称代词 he, she, they 或one(s), anyone, nobody 等时
He who plays a trick must be prepared to take a joke. 玩花招的人必定会受到戏弄。
The ones who refuse to reform should be punished as required by law. 拒绝改革的人应依法受到惩罚。
It was she who first introduced me to the pleasures of wine-tasting. 是她第一个让我领略到品酒的乐趣。
There is nobody who has no shortcomings. 没有缺点的人是没有的。

2) 当先行为指示代词 those，或先行词是those所修饰的人时
This website is dedicated to those who died in the war. 这个网站是献给那些在战争中死去的人。
She is one of those women who always make the worst of their troubles. 她是那些老是把困难往最坏处想的女人之一。

3) 当先行词是序数词或被序数词修饰时
He is the third man who witnessed the murder. 他是这起谋杀案的第三个见证者。
They were the first who were there. 他们是去那里的第一批人。

4) 当先行词是 people 或是表示人的集体名词时
An interactive product should show interest in the people who use it. 一款互动的产品应该展现出对用户的兴趣。
The crew who were all asleep forgot to hoist a lantern. 已入睡的船员全部忘了挂起提灯。

5) 当先行词与定语从句被其他句子成分隔开时。（更多这样的例子可见隔离定语从句一文)
He is the only doctor in this hospital who I trust. 他是这家医院里我唯一信得过的医生。

6）当关系代词在从句中作主语且与谓语动词被分隔开时
He was a man who, if had been properly supported, would have worked wonders. 他是一个本该创造出奇迹的人，如果当时给予适应的支持的话。

7) 当表示人的先行词由两个定语从句重叠修饰时(即双重定语从句)，第二个定语从句只能用who/whom引导，而不能用that。而且第二个定语从句的引导词不能被省略。
The only person I know who has a skeleton in the cupboard is George Carlton. 我所认识的唯一的在柜中藏骷嵝的人便是乔治. 卡尔顿。

Answer 2

如果主句中的主语是that的话，为避免重复，用who引导后面的定语从句。如：
That is the man who want to meet you.