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The spatial distribution quality of straw in the soil has a significant effect on the decomposition rate of straw and the distribution of soil nutrients. To explore different rotary tillage operation parameters on the quality of the straw spatial distribution, simulation model of rotary tillage straw returning rotary tillage operation simulation process was built based on the discrete element method, and combined with field experiment with different speeds and qualities of straw spatial distribution of the knife roller speed comparison to test and verify. The simulation and field experiment areas were divided vertically and horizontally, the number of straw in each area was calculated, and the spatial distribution quality of straw under different rotary tillage operation parameters was evaluated using the coefficient of variation of straw ratio as the index. The results showed that in vertical stratification, the variation coefficient of straw ratio in each layer was increased with the increase of cutter roll rotation speed, and the minimum value was at 240r/min, and the simulation value and test value were 60.09% and 80.65%, respectively. However,，with the increase of advancing speed, the coefficient of variation was decreased at first and then increased, and the coefficient of variation was the smallest at 0.50m/s, and the simulation value and experimental value were 61.00% and 79.90%, respectively. In the horizontal division treatment, the increase of cutter roll speed had no obvious regular effect on the variation coefficient of straw proportion in each layer, but the increase of advance speed could reduce the variation coefficient in the longitudinal division area, and the minimum value was 11.36% and 20.12% at 0.75m/s. The variation trend of simulation value and field value was basically consistent. The maximum mean difference between simulation and test values of vertical distribution and horizontal distribution was 22.13% and 12.23%, respectively, and the error was within the acceptable range. The discrete element simulation can simulate the spatial distribution of straw under different rotary tillage operation parameters, which can provide support for the rapid prediction and evaluation of straw returning operation quality. It can also provide a theoretical basis for the selection of operation parameters of rotary tiller.