Abstract: Polyvinyl alcohol(PVA) with high molecular weight and high purity is rather difficult to be bio-degraded in the natural environment and to satisfy the requirement of self cleaning of the water system.For improving its biodegradability,hydrogen peroxide and Fe²⁺ system is used to oxide the hydroxyl groups of PVA,thus facilitating the breakage of the main chain of PVA.The oxidative modification reaction conditions are determined through studying the dynamics of oxidation and measuring the molecular weight.Infrared spectrophotometry study has proved that oxidative reaction has rendered PVA the ketone-ketone structure which is necessary for biodegradation,and ultraviolet spectrophotometry is used to determine the biodegrability of the modified PVA.The results indicate that proper oxidation of PVA can significantly improve its biodegradability.