The aerodynamic performance of the tip leakage flow of flat tip and cavity tip was investigated numerically in transonic turbine cascade. The Mach number within the tip gap of flat tip was higher than that of cavity tip. Oblique shock wave structure appeared within the tip gap of flat tip. For cavity tip, the oblique shock wave structure was not obvious because of low Mach number within the tip gap. The mass flow ratios of tip leakage flow to the mass flow at the inlet of the cascade for flap tip and cavity tip were 3.87% and 3.74%, respectively. The aerodynamic loss coefficient was 0.079 for flat tip and 0.072 for cavity tip. The study shows that the aerodynamic performance of cavity tip is better than that of flat tip.