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Aiming at the existing heavy-duty precision planter soil-covering device at high speed, there are problems such as high impact on seed spacing uniformity, seed being overhead, etc., the proposed combination of Archimedean spiral-type and extruded soil cover technical ideas, an Archimedean spiral-type arc double-toothed disc soil-covering device was designed, to achieve suitable and uniform mulch thickness and reduce the impact of mulching operations on seed spacing uniformity. The structural parameters of the mulching device and the amount of mulch were analyzed, and the range of values of the main parameters affecting the effect of mulching was determined;the simulation and optimization analyses of the designed components were carried out by using EDEM software to determine the optimal parameter combinations of the arc double-toothed disc;and the operational performance of the device was verified through field experiments. The results showed that the main structural parameters affecting the operational performance of the arc double-toothed disc were the center distance, installation inclination, and embedded depth of the arc double-toothed disc. When the center distance of the arc double-toothed disc was 142.6mm, the installation inclination was 20°, and embedded depth was 55mm, the device passed well with suitable and uniform mulch thickness, the average mulch thickness was 47mm, and the standard deviation and coefficient of variation of qualified spacing differed from the blank control group by 0.22mm and 1.81 percentage points, which was a small influence on the uniformity of sowing and met the agronomic requirements of precision sowing.