High toughness integrated with self-lubricity of beta-Sialon composites at elevated temperature containing second phase particles were successfully fabricated. It was found that the fracture toughness can be substantially improved by addition of Cu powder. The fracture toughness can be reached 6.75 MPa m(1/2) and 4.42 MPa m(1/2) at 25 and 900 degrees C, respectively. Meanwhile, the tribological properties of Cu-doped Sialons have a tremendous improvement at high temperature. Especially when the content of Cu powder is above 10 wt%, the wear rate decreases by two orders of magnitude and the friction coefficient reduces to 0.56-0.65 at 900 degrees C. In addition, the microstructure of composites was characterized, and crack propagation behavior and tribological behavior were discussed to clarify the toughening mechanisms and self-lubrication mechanisms. The results show that the principal toughening mechanisms are crack deflection and crack bridging. The tribo-chemical reaction and generated CuO films with lubricity are the main self-lubrication mechanisms.