fumei, my understanding is that the OP wants the number in the header to be the page number in the section, and in the footer the page number in the document.

This is not possible directly in Word but there is at least one Work-Around.

This is to put a hidden SectionPages field in each section. That needs to be bookmarked. Then a calculation field is used for the Footer page numbering. It adds the current page number in the section (the one displayed in the header) to the bookmarks for the previous section. This will require a different footer (or footers) for each section.