Abstract: The effect of pH and dialdehyde starch ( DAS) on the mechanical properties and water resistance of edible gelatin films prepared from tilapia skins was investigated. With increasing pH of film- forming solution, the tensile strength ( TS) of films firstly increased, but a decrease of TS was observed after pH7, where the maximum TS of 23.78MPa was found.However, the matter solubility ( MS) and protein solubility ( PS) of gelatin films decreased gradually with increasing pH.The TS of gelatin films increased when incorporating DAS into film- forming solution, while their MS and PS declined significantly.On the other hand, the mechanical properties and water resistance of films were effectively improved by adding 1.5% DAS at pH7.Based on the SDS-PAGE analysis, no obvious change in the gelatin components was found at different pH during the film forming process, and the crosslinking between gelatin proteins was mainly induced by DAS.