In view of the unreliable operation of the V-type extrusion soil-covering device under clay conditions, the seed furrow is not tightly closed, which is easy to cause the actual production problems of seed “overhead” and “seed drying”. A star-toothed spherical disc soil-covering device was designed to improve the soil covering quality of the planter. The working principle of the star-tooth spherical disc soil-covering device was analyzed. Through the kinematic analysis of soil particle in the process of soil covering operation, the main structural parameters affecting the quality of soil covering operation were determined, and the main structural parameters and installation parameters of the star-tooth spherical soil-covering disc were designed. The interaction model between soil and soil-covering device was established by using EDEM. The single factor and Box-Behnken tests were carried out with the installation inclination angle, installation distance and penetration depth of the star-tooth spherical disc as the test factors, and the weight of the covering soil and the coefficient of variation of the covering soil weight as the evaluation index. The optimal structural parameter combination of the star-tooth spherical soil-covering disc was determined as installation inclination angle of 25.03°, installation distance of 196.66mm, and penetration depth of 77.65mm. A field validation test was conducted under this parameter combination. The field validation test was carried out by taking the installation inclination angle of 25°, installation distance of 197mm, and penetration depth of 77mm. The test results showed that the average weight of covering soil was 241.46g，which was consistent with the simulation results, and the relative error was 5.12%.The coefficient of variation of the covering soil weight was 3.71%. The weight of covering soil was uniform and the operation quality was good. The seed sowing depth met the agronomic requirements after the soil covering operation. The star-tooth spherical disc soil-covering device can effectively improve the soil-covering performance of the planter.