Abstract: In order to significantly improve the mechanical properties and thermal endurance of poly(butylene succinate), the micron hexagonal boron nitride (h-BN) was treated with silane coupling agent KH550, and blended with PBS to modify PBS. The high thermal endurance h-BN-KH550/PBS composite films were prepared through melt blending and rolling mill process. The particle structure of h-BN-KH550 and the mechanical properties, aggregation state structure, fracture morphologies, crystallization property and thermal stability of composite films were investigated. The results reveal that the mechanical properties of h-BN-KH550/PBS composite films are greatly improved compared with PBS. When the mass ratio of KH550 to h-BN is 2:50 and h-BN-KH550 to PBS is 3:50, the comprehensive mechanical properties are optimal. The h-BN-KH550 particles are well dispersed in PBS. During the crystallization process of PBS, h-BN-KH550 can act as nucleating agent and increase the crystallization rate and crystallinity of PBS. The thermal stability of h-BN-KH550/PBS composite films is significantly increased. When the mass ratio of h-BN-KH550 to PBS is 3:50, the temperatures at 5%, 10%, 50% mass loss (T₅^d, T₁₀^d,T₅₀^d) and the peak of pyrolysis temperature (T_p) are increased by 30.0, 22.6, 9.5 and 10.0 ℃ during the pyrolysis process of composite films, respectively.