Softwares are:snagit with snagit editer;virtual pdf printer !
Open the large size picture(mines are always longer than one page)with snagit editer,then configure the page setup in the print option,choose "fit the width."
then send print to the virtual pdf printer,of course you should install before above steps.
I'm so happy that I solve the problem in a way,
The inspiration comes from the installed software PDF-Xchange3 (actually this is installed with other software)
The pdf saver 3 with his pdf printer(another printer)can also help you save the pdf document with two or more pages that splitted from the large picture.
but the editon I use have some warter marks,so I give up it.
Microsoft Office OneNote 2007 can also help you print,but it maybe not so easy to batch process.
Snagit is the most important,Let me proceed to research how to batch process easily.
I'd like to know other easy methods！Thanks for your sharing.
If someone have the same problem,I'll link some pictures if you need.