广西建筑模板价格表:为什么要用两个That?

He said that.....他说。。。。
that作连接副词，引导宾语从句。省略号处应该加入一个完整的句子。

That was an excellent idea.是一个完整的、有主谓宾的句子，这里的that作名词，是句子的主语。

连起来，He said that that was an excellent idea.两个that都是句子的必备成分，都不能省略。

第一个that是宾语从句的标志，不能省略。第二个that是从句的主语，也不能省略。

He said that that was an excellent idea.

第一个“that”作指示代词，指代说话人的指向，作主句的宾语。
第二个“that"是引导词，引导一个从句。

第一个that是连接副词，引导从句；第二个that是代词，代的是说话者与听话者都知道的一件事。两个that都不可省略.

怎么都会这么解释…………其实这个句子有个that可以省略的啊！He said （that）that was an excellent idea.确实，第一个that是宾语从句的标志，是连词。但大家都需明白一点：不省略当然是对的，但是一般在日常交流中这个连词that可以完全省略。但大家要注意一个省略前提：那就是后面的从句开头若是是副词短语或其他非主语成分的话，这个that最好不要省略，因为会引起歧异。但楼主的这个句子不会，因为从句主语是代词that，"那个"的意思。所以这个句子可以完全省略成He said that was an excellent idea.只是若是口语表达，建议在he said后面稍微停顿一下，这样意思就非常明确，可比2个that清楚地多。本人一直这么使用，好像考过八级至今，无论老外、中国人都未对此用法有过什么意见。英语就是用的，不要死拘泥于语法，中国的英语可以考死外国人的！！！

He said that that was an excellent idea.
the first that can refer to what he said..
but the second that refer to the excellent idea

if change the sentence to he said that was an excellent idea. it only emphasise his opinion on the idea which is excellent. but if you add another that, it will also stress on what he being said and also the command he made which is the "excellent idea"