Abstract: The structures and performance of starch were modified by microwave radiation,which is a high efficient,energy saving and harmless technique.It was obviously observed that the microwave radiation changed the morphology and structure of starch particles.It was proved by the intrinsic viscosity test of starch that microwave radiation caused high frequency vibrations of the starch macromolecules,leading to fracture of glycoside bonds and degradation of macromolecules.The behaviors of sizing pastes and films of the starch,natural starch,oxidative starch and hydrolyzed starch radiated by microwave were also tested.The results indicated that the viscosity of sizing paste decreased after the starch was radiated by microwave and the decrease level was related to the duration of microwave radiation.And its adhesion to the fiber was also improved after microwave radiation.The breaking strength,elongation,abrasive resistance,flexibility and wettability were close to or higher than those of oxidative starch and hydrolyzed starch.