Abstract: The development of biodegradable plastics holds significant importance and value in achieving carbon peaking and carbon neutrality goals. Utilizing gelatin as the raw material, gelatin films were produced through a combination method involving plasticizing with nonanoic acid, crosslinking with dialdehyde starch, and hot pressing. Investigation was conducted to explore the effects of nonanoic acid plasticizing and hot pressing on the structure and performance of dialdehyde starch-crosslinked gelatin films. Results indicate that, when a 20% addition of nonanoic acid was made, the modified gelatin films exhibited a smooth surface, dense structure, the highest tensile strength, and lower rates of elongation at break, water vapor permeability and swelling properties. After 11 minutes of hot pressing, the gelatin film demonstrated improved water resistance and mechanical properties. It maintained a relatively intact film morphology after 22 days of degradation in soil, and over 80% mass loss after 34 days. The gelatin films prepared through nonanoic acid plasticizing, dialdehyde starch crosslinking, and hot pressing, with high mechanical strength, water resistance and environmental degradability, are offered beneficial strategies for the development of environment-friendly protein plastics.