Abstract: The turbine is the core equipment for realizing heat-power conversion in the thermodynamic cycle. Optimizing its geometric parameters to enhance its aerodynamic characteristics is an efficient approach to boosting the thermal efficiency of the entire cycle system. Drawing from the design parameters of the supercritical carbon dioxide turbine utilized in waste heat recovery for marine main engines, we have achieved the calibration of key geometric parameters for the high-speed radial-inflow turbine. Using the CFX simulation method coupled with the real physical parameters of CO₂ in the database, the influence laws of geometric parameters rotor, stator blade wrap angle, and impeller outlet geometric angle on the performance of the turbine are analyzed in detail. The operation characteristics of the radial-inflow turbine under the off-design operating conditions are further studied. Simulation results indicate that increasing the wrap angle of stator blade will cause disturbance eddy current at the leading edge of rotor blade and reduce exit loss. With the increase of impeller outlet angle, the influence of the rotor blade wrapping angle on turbine efficiency remains unchanged, but the peak point of isentropic efficiency will move along the direction of the rotor blade wrap angle decreasing. Through optimization analysis, the isentropic efficiency of the turbine design point is 87.99% when the wrap angle of the rotor and stator blades and the geometric angle of the impeller outlet are 49, 21.5, and 25, respectively, which is 0.54 percentage points higher than that before optimization. The isentropic efficiency of a radial- inflow turbine is more than 80% when it deviates from the design point by 20% up and down. The results can provide reference for the design of the supercritical carbon dioxide high-speed radial-inflow turbine.