The effect of the temperature at the friction surface on spheroidization and refinement of Si particles in hypereutectic Al-30Si alloys was investigated. Al-Si samples as cast were first preheated to 15°C, 100 °C, 300 °C and 500 °C, respectively, then rubbed against a steel counterface for 5 min under a normal pressure of 50N. Refined layers where all the Si particles were broken to 0.71-0.87μm in diameter and spheroidized simultaneously to 0.69-0.74 in shape factor were found in the friction surface of the samples. As the preheating temperature increased, the refinement effect was gradually weakened, and the spheroidization effect was enhanced. The reason of the simultaneous spheroidization and refinement were discussed.