Abstract: Based on the experimental data of a small backward bend duct buoy（BBDB）,4 radial turbines are designed to study the influence of blade shape on the energy conversion efficiency of radial turbines used for wave power generation. The performance parameters of the 4 turbines in steady flow are obtained by numerical analysis. Results show that performance of the 4 turbines is similar.Based on the numerical analysis results in steady flow,performance of the 4 turbines in unsteady flow are analyzed by using the quasisteady analysis method. Results show that efficiency of the 4 turbines in the unsteady flow is different due to the reverse flow. Therefore,to design the air turbine used in BBDB should consider not only the efficiency but also the torque generated by reverse flow.