The biodegradable plastic film was prepared by blending canna edulisker starch(ST)with polyvinyl alcohol(PVA),and crossing linking agents,such as formaldehyde,gelatin,borax.The suitable process conditions of preparing the plastic film having good water resistance and mechanical properties were determined.The stretching strength of this film is 15.19～17.97 MPa,and its extension rate is 72%～151%,which surpasses the GB4456 84 standard.The water absorption rate is 36%～61%.This film is a polymeric new material nowadays,with a low cost,availability and selfdegradability.It provids a reliable approach for resolving the pollution problem of plastic wastes.