The normal double column mechanism tries to place a graphic, stores it when there is no place, and flushes it as soon as possible.
The \startcolumns mechanism works well intermixed with the standard one column mode.
In your case, esp for vertical chinese, use columnsets:
\startcolumnset
\placefigure[tblr:1]{}{} \placefigure[tblr:2]{}{}
\input tufte
\stopcolumnset
This will place the floats on top of the first and second column; an alternative usage is:
\placefigure[tblr]{}{} \placefigure[tbrl]{}{}
Think of tb meaning flush from top to bottom, and lr to mean from left to right; so, there are quite some ways to place/flush a graphic.
Thanks. It place the figures side by side correctly. But, there is another problem. After the two figures, it force a page break and leave a large blank even though the blank area can accommodate the next paragraph. I attached the test file and waht I really want is: One column texts two figures sidebyside One column texts Thanks. Wang