In recent years, with the development of manufacturing technology and production capacity, wind power industry has been developed rapidly.A new type of pin-cycloidal planetary reducer was proposed in this studyfor the actuator of the pitch of high-power wind turbines. Based on the transformation mechanism method, the transmission efficiency of the reducer was calculated by analyzing the pin-cycloidal meshing efficiency, bearing efficiency, and output mechanism efficiency. Prototype testing were combined to systematically and deeply study the design theory of the reducer for the pitch of high-power wind turbines. Finally, a new design was proposed for a reliable two-stage pin-cycloidal planetary reducer with a strong bearing capacity and multi-tooth meshing on the hard gear surface that can be applied to the pitch system of high-power wind turbines.