In order to optimize the structural type of the rotor blades of radial flow turbine to improve effectively the turbine’s efficiency, a three-dimensional transient whole-basin numerical model is constructed for the radial impact-type turbine with impulse rotor blades in oscillating water column wave energy convertor based on the Ansys-Fluent software. By changing the suction surface type of the turbine’s rotor blades, the influences of the thickness difference of the rotor blades on the parameters such as turbine torque and pressure and the unsteady performance evaluation parameters such as turbine input coefficient, torque coefficient and periodic average efficiency are studied under the sinusoidal reciprocating incident airflow condition. Under the condition that the pressure surface type is guaranteed unchanged, the unsteady working performances of the turbines respectively with a rotor blade thickness of 7 mm, 13 mm, 16 mm, 19 mm and 22 mm in the inhale and exhale stages are studied. The results show that the turbines with different rotor blade thickness have a large difference in their unsteady working performances, of which the turbine with a rotor blade thickness of 13mm has the optimal working performance, with its maximum peak efficiency being up to 47.7%.