OK, its behavior is same as what I expected.
These words can only be found when they are separated by spaces, that's 
why I can got result when I search "你好" "谢谢" or "欢迎".

Usually we don't put unnecessay spaces in the normal sentence, so the 
bug is that roundup is not able to search the Chinese word in the 
sentence in "All text" search func.

But as I tested, it works well when I use the "title" search func, yes, 
it do find match when I search Chinese word from the sentence in the 
tilte area(without spaces).

So, How can we let roundup "All text" search behave in the same way as 
"Title" search?

Thanks!