Abstract: The fracture properties such as fracture toughness,K_1c,and crack extension force,G_1c in a series of short carbon fibre (CF) reinforced polyarylethersulfone with cardo groups (PES-C) composites with different CF content have been measuerd.Meantime,the fractal dimensions D_f, of fractured surfaces have been determined by means of slit island method. The results show that D_f decreases smoothly with the increasing of lnG_1c. An analysis of relationship between C_f and G_1c was given on the basis of fracture micromechanism of composite.