Aluminum film explosive was obtained by replacing aluminum powder in traditional aluminized explosives with aluminum film. The pressure-time curves at different position for composite explosives with aluminum film content of 10%-40%, and RDX were obtained by underwater explosion contrast experiments. The peak pressure, impulse, specific shock wave energy and specific bubble energy were obtained via analysis and calculation of the curves. When aluminum film content is 10%, the impulse of aluminum film explosive relative to RDX increases by 9%-9.5% and the specific shock wave energy relative to RDX increases by 9%-12%. The effect of aluminum film content on underwater explosion performances of aluminum film explosive is different from that of traditional aluminized explosive, which is caused by the grain structure of aluminum film explosive and the reaction extent of aluminum film.