To address the rapid heat dissipation， difficulty in sustaining combustion， and unstable energy release of energetic films under the strong cooling effect of water， Ti/poly（vinylidene fluoride） （Ti/PVDF） composite energetic films with different Ti contents were prepared by solution blending followed by freeze-drying. Their structural characteristics， wettability， thermal behavior， and ignition/combustion performance in air and underwater environments were systematically investigated. The results show that Ti particles were effectively incorporated into the PVDF matrix， while the characteristic crystalline structure of metallic Ti and the fluoropolymer structure of PVDF were retained， providing the structural basis for exothermic reactions between Ti and fluorinated decomposition products. Compared with air， the rapid heat transfer and strong cooling effect of water markedly increased the ignition difficulty and strongly influenced combustion propagation and energy release. At low Ti contents， the heat generated by the system was insufficient to compensate for heat loss to the surrounding water， making effective ignition difficult. As the Ti content increased， the apparent heat release increased and the underwater ignition and sustained reaction capability were enhanced. Meanwhile， the continuous film-forming and encapsulation effects of PVDF weakened， resulting in reduced hydrophobicity and more pronounced water contact and cooling of the reaction zone. Under the combined influence of enhanced heat release and intensified water cooling， the film containing 50 wt.% Ti exhibited better combustion sustainability， whereas the 60 and 70 wt.% Ti films reacted more rapidly and generated pronounced bubbles and surface disturbances. Overall， the 50 wt.% Ti film is more suitable for applications requiring sustained and stable combustion， while the 60 wt.% Ti film is more favorable for rapid and concentrated energy release.