Abstract: In order to study the mechanism of spiral drill subsoiling, the evaluation indexes of soil particle movement velocity, particle mixing degree, stacking angle, soil tillage resistance, fluctuation coefficient and subsoiling power consumption were put forward. Combining the three-dimensional model of spiral drill and the discrete element model of soil, a spiral drill-soil model based on discrete element is established. Selecting reasonable motion parameters, the process of subsoiling by spiral drill is simulated by discrete element method. The effect of subsoiling and the influence of spiral drilling on soil are analyzed. Based on the control variable method, nine groups of orthogonal simulation experiments under different tillage depth and different tillage velocity were designed. The subsoiling effect was comprehensively evaluated and the influence law of tillage depth and tillage velocity on subsoiling effect was summarized. The results show that the tillage velocity has a great influence on the subsoiling effect, and the lower tillage speed should be selected as far as possible on the premise of breaking the bottom of the soil plough in actual working conditions. The mechanism of subsoiling is revealed, which provides theoretical basis for spiral drill subsoiling soil.