A fitting curve subsoiler was designed aiming at the problems of large soil disturbance and large tillage resistance caused by subsoiler in sub-soiling site preparation work in Northeast China. The discrete element (EDEM) software was used to simulate the movement of the tip of a subsoiler in the soil. Through calculating, the fitting curve and fitting equation were obtained from the trajectory of soil particles above the tip of shovel. After summarizing, the method of line element design was used to optimize the alignment to acquire the curve of shovel handle shape, meanwhile, to design the edge, lip and penetration angle were cut. Then the interaction effect test of shovel handle and shovel tip were used to prove the feasibility and rationality of the design. The contrast test of soil trough showed a fitting curve subsoiler can effectively reduce the soil disturbance and tillage resistance. Compared with polygonal subsoiler, the fitting curve subsoiler made the soil disturbance reduced by 53.6%, tillage resistance reduced by 36.23%. Compared with circular subsoiler, it made the soil disturbance reduced by 66.18% and the tillage resistance reduced by 29.18%. Compared the fitting curve subsoiler with the polygonal subsoiler with field experiment, it was showed that using the fitting curve subsoiler made the soil return area increased by 81.03%. Compared with circular subsoiler, the fitting curve subsoiler made the soil return area increased by 146.95%. Both the soil trough experiment and the field experiment verified that the fitting curve subsoiler can make the soil disturbance smaller and tillage resistance smaller, which met the requirements of sub-soiling operation.