Abstract: Peroxid and free radical are created when starch is radiated by gamma ray.Grafting action can be tested by infrared spectroscopic analysis,when γ-radiated starch is gelatinized with polyacrylamide together.This action maybe concerned with peroxide decomposed and the Hofmann action of polyacrylamide.Moreover,different gelatinization makes different viscosity,high-pressured size mixing has higher viscosity,but viscosity stability is ensured under the identical gelatinized condition.