Qt program with libtiff functions

So I was trying to cross compile my qt program for s3c2440, a platform based on ARM9 processor. During compilation, I got "tiffio.h: No such file or Directory" error, when I add the libtiff path to includepath I got "TIFFOpen: undefined reference","TIFFClose:undefined reference" etc. So I add a link flag "-ltiff" into Makefile of my project, and the compiler tells me it "cannot find -ltiff"... During configuration of qt, I am pretty sure I have added the option "-qt-libtiff" or "-system-libtiff"... I am running out of way, anyone could give me some help? Really appreciated.