Abstract: The thermal and tribological properties at high temperature of polyimide (PI) composites were improved by enhancing the heat resistance and thermal conductivity. Cage polysesquiloxane (POSS) and SiO₂ were selected to improve the heat resistance, carbon nanotubes (CNTs) and Cu powder were chosen to improve the thermal conductivity. Then, molecular simulation and experiment were both used to study the effect of each component on its properties. The results show that POSS and SiO₂ could improve the heat resistance and Young's modulus of PI, but reduce the thermal conductivity and impact strength. Cu improves the high temperature resistance and thermal conductivity of PI, but reduces the mechanical strength. CNTs show an excellent reinforced effect at low content, but become worse at high content. Then, PI composites modified by the multi-component were designed according to the results of single-component modification. The results show that the PI composites with 3wt% POSS, 3wt% SiO₂, 0.5wt% CNTs and 3wt% Cu have the best comprehensive performance and the best friction performance at high temperature. The friction coefficient at 200℃ is 0.65, which is 27.8% lower than that of pure PI. The wear rate is 5.11×10⁻⁵ mm³/(N·m), decreasing by 19.3%.