The water-swollen films of poly(vinyl alcohol) were crosslinked via electron-beam irradiation to form transparent hydrogel films, The material we obtained was weak and easily shattered. After slow dehydrating at room temperature then heating at 120~160℃ for 1~2 hours, it was reinforced due to induction of partial crystallization. The degree of crystallinity varies from 25% to 43%. The measurement of the mechanical properties of the crystallized hydrogel films showed that modulus and ultimate strength were improved.