From looking at your site index you only have one page called
syntax. It's
zh:wiki:syntax - and it has
no content (so you can't link to a header in it called
sec).
To make the link on
zh:test work you'd need to:-
1. change the second link's code to
[[zh:wiki:syntax#sec|sec2]]
2. add a header called
sec to
zh:wiki:syntax =====sec=====
But I'm not certain that's what you actually want to do (sorry, I can be a bit thick, and I'm listening to this with a screen reader which creates other problems).