Aiming at the performance requirements of rotary reducer in the field of photothermal power generation, such as external structure, high rotary precision, high protective performance and self-locking function, a rotary reducer with high transmission precision, flexible rotation, high protective performance, self-locking function and compact structure is designed. During the design process, various factors affecting the transmission accuracy of the reducer are analyzed in detail, and the materials of the parts are reasonably selected according to the influencing factors. Through theoretical calculation, the influence of the backlash of the worm gear pair and the tooth thickness tolerance of the planetary gear pair on the backlash is obtained. The calculation results show that the transmission accuracy of the reducer meets the requirements within the tolerance range of each influencing factor; On this basis, the protection performance of the rotary reducer is strengthened, and its protection level reaches IP65. After the prototype is completed, the performance of the rotary reducer is tested. The test results show that the performance of the reducer meets the design requirements, which provides a basis for the design and development of similar products.