This work presents, for the first time, data on the possibility of synthesizing polyimide nanocomposite films based on track nuclear membranes and organosiloxane (polyhedral oligomeric silsesquioxanes) POSS structures. The synthesis of the nanocomposite films was carried out by filling the tracks of a polyimide membrane with POSS structures under hydrothermal conditions in a high-pressure reactor. The surface and mechanical characteristics of the developed nanocomposite films were studied, and the results of their resistance to the flow of oxygen plasma are presented. It was found that the introduction of POSS structures significantly increased the resistance of polyimide to the flow of oxygen plasma. The PI/POSS composite exhibited an insignificant change in weight, the weight loss reached 0.92 ± 0.05 mg/cm 2 in 24 h after the start of the experiment, which is almost two orders of magnitude lower than that of the polyimide film.