I'm writting to tell you something I don't think is good？

应该改为：I am writing to tell you something that I don't think is good.

=I am writing to tell you something (I don't think that is good)

继续跟踪回答如下，

有人认为something后是定语从句，在从句中作主语，所以需要that,您怎么看？

something 在定语从句中作宾语可以省略，如果在定语从句作主语，则不可以省略。明白了吗？

(1)I have something that I want to tell you（作宾语）

(2)Something that is important needs to be solved first.（作主语）

我知道，您好像没明白我的意思。问题是有人认为something后面的句子是定语从句，需要that指代something，并在从句中作主语，所以不能省略that。

跟踪回答如下

something that 结构，是关系代词在定语从句作主语不可以省略，作宾语可以省略，不是现行词something作主语或者宾语啊！

Something （that he told me） is very important.

something 在主句作主语，但是关系代词that在定语从句是作宾语啊！

I have something that needs to be solved immediately.

I have something that has confused me for a long time

something作宾语，that 作主语，

I have something that I have not solved.

something作宾语, that作宾语

I'm writting to tell you something I don't think is good？

something 后面的 that 需不需要?

公元2017年12月21日继续跟踪解答如下

(1)I am writing to tell you something  (that I don't think is good)（关系代词that的定语从句）=I am writing to tell you something (I don't think that is good.)

解析：that代替前面先行词something宾语从句作主语成分。)

(2)I am writing to tell you something that is good.（关系代词that的定语从句）

解析：定语从句that is good修饰直接宾语，that 代替先行词something

(3)I am writing to tell you that something is good.(连词that宾语从句）

解析：that something is good为宾语从句作动词tell的直接宾语。