Abstract: Four series of polymeric drugs with 5-Fluorouracil(5-FU) cova-lently linked in side chain were synthesized by the use of starch and carboxylmethylcellulose and two new 5-FUderivatives were also synthesized by using molecular sieve as a catalyst.Their structures were determined by IR,¹H NMR and mass spectra.The changes in the Nitrogen content of polymeric drugs with reaction conditions and the influences of the Ncontent on their limiting viscosity were studied.The hydrolysis of 5-FU from starch and carboxylmethylcellulose derivatives in various of buffer were researched by simulating physiologically acid-alkali enviroment.In addition,anticancer activity(in vivo and in vitro) of some starch derivative has been preliminaryly observed.