The flow condition between the rotor blades of a liquid rocket engine supersonic turbine was studied experimentally and numerically. The entrance Mach number was 1.94, and the turning angle of the blades was 120&#176;. A shock wave was created at the leading edge of the blade, and the Mach number in the passage between the blades decreased to around unity. A similar deceleration has been reported in several past studies. It was found that centrifugal force created the shock wave at the leading edge, reducing both the Mach number and total pressure. This phenomenon is characteristic of high-speed blades with large turning angles. The Mach number in the passage was restricted when the mass flow rate was specified under the specified passage configuration. A convergent-divergent configuration of the passage between the blades suppresses the performance degradation of supersonic turbines.