Microstructure of Al-Ti-C master alloy prepared by liquid-solid reaction method were observed through SEM analysis,and the optimized scope of chemical composition was determined through the comparison of the refining effects of Al-Ti-C master alloy with various ration of Ti to C.The nucleation undercooling rate of aluminum melt,the driving force of nucleation and growth and refining mechanism of alpha aluminum phase during solidification were analyzed.The results showed that refining effects is dependent on the comprehensive role among TiC quantity,nucleation activity and the restrained factors for grain growth.