A rotary-cut micro-ridge seedbed preparation device (RMSD) was designed to facilitate rapeseed direct seeding in the mid-lower reaches of the Yangtze River region, where continuous rainfall and sunny days can cause significant fluctuations in soil moisture and affect seedling growth. The RMSD employs rolling boards that passively rotate and stack micro-ridges by cutting into the rotary-tilled soil as the machine moves forward, with grooves connecting to furrows on both sides. The geometric size of the micro-ridge was defined according to the row spacing configuration and root growth characteristics of direct rapeseed seeding, combined with soil water and ridge cultivation heat characteristics. Based on kinematics, the rolling board endpoint trace and the rolling board envelope were analyzed to determine the qualitative parameters in the structure terms. The results were that the number of rolling boards was 6~10, and the angle range of the rolling board was 0°~28°for further study. The DEM-MBD coupling simulation was conducted with the single factor test and the orthogonal rotation regression test to investigate and optimize the parameters of the RMSD (rolling board number, rolling board angle, and forward speed). The optimization results were as follows: when the rolling board of the RMSD was 6 and 8, respectively, and the rolling board angle, rotary cutting depth, and efficient groove depth were 28.00°, 100mm, 83.59mm and 26.50°, 92mm and 64.26mm, respectively. The field test used the Trimble TX8 3D laser scanner to reconstruct the micro-ridge surface after RMSD operation and compared it with the simulation results. The field test showed the maximum deviations of actual depth and micro-ridge distance were 8.25%, and the qualified rates of micro-ridge were 100% and 90%, respectively, under the optimal parameter combination of 6 and 8 rolling boards. The research result can provide a reference for the structural improvement of the rapeseed bed preparation device.