on which一般表示在某个地方或具体时间的某一天，而in which则侧重于表示一种所属关系或场所、状况。
on which 与in which 有什么区别
1、指代不同
1、in which：在其中。
2、on which：什么。
2、侧重点不同
1、in which：侧重于表示一种所属关系。
2、on which：侧重于表示一种目的关系。
3、引证使用方法不同
1、in which：which用作疑问代词时，在特殊疑问句中用作宾语或主语。
2、on which：which用作关系代词，可引导限制性定语从句或非限制性定语从句。
4、使用方法不同
“on which”和“in which”都可以用来引导定语从句，修饰先行词，不同在于介词的用法，取决于先行词的搭配，比如“The hotel, on which we stayed last year, was very comfortable ”（大家去年住的酒店很舒适）。
而“in which”一般表示在某个场所或状况下，比如“The house, in which he grew up, was very old and beautiful”（他成长起来的房屋很古老而漂亮）。
介词加which的使用方法
1.in which 在……里面
The school he once studied in is very famous.
= The school in which he once studied is very famous.
2.for which 为了……目的 Tomorrow I will bring here a magazine you asked for.
= Tomorrow I will bring here a magazine for which you asked.
3.on which 在……的上面或具体时间的某一天
I have a dresser in my bedroom, which there are many cosplaymetics on.
= I have a dresser in my bedroom on which there are many cosplaymetics.
4.at which 在……里面或在……上面
The dumpling House which he often has dumplings at is very popular.
= The dumpling House is very popular, at which he often has dumplings.
which放在句首的意思是
当"which"置于句首时，一般是为了引导一个非限定性定语从句，用于进一步描述或讲解先行词（即在主句中出现的名词）。
非限定性定语从句用来提供关于先行词的额外信息，但并不对先行词进行限定。这一般与用"that"引导的限定性定语从句形成对比。
以下是一个示例：
主句：I bought a new car.
非限定性定语从句：which is blue.
合并后的句子：I bought a new car, which is blue.
在这个例子中，"which"引导的非限定性定语从句："which is blue"提供了对"car"的额外描述，即它是蓝色的。整个句子的意思是，主语购买了一辆新车，而且这辆车是蓝色的。
应该注意的是，非限定性定语从句常常用逗号与主句隔开，在句子中起到补充说明有哪些用途。而限定性定语从句则没逗号，对先行词进行限定，意义上更为必要。
