To solve the problem that the threshed outputs on the sieve surface of the crawler-type rape combine harvester commonly used in the main oilseed rape producing areas in the Yangtze River basin is prone to accumulation and stagnation when harvesting high-density and high-yield rape, which affects the penetration of oilseeds through the sieve and leads to a high loss rate and low operating efficiency, an uniform dispersion diversion device for material movement on the sieve surface was designed by analyzing the material dispersion movement law during the cleaning process, and the key operating and structural parameters of the device that affect the operating performance of the cleaning system were determined. Based on the coupling method of CFD-DEM, a quadratic regression orthogonal combination test method was used to carry out parameter combination simulation optimization test with oscillation frequency of diversion rod, rotation speed of diversion rod and drive joint chute inclination angle as test factors, and cleaning loss rate and cleaning impurity rate as performance evaluation indexes. The results showed that each factor had a significant effect on the performance evaluation index, among which the most significant effect was on the oscillation frequency of diversion rod. The optimal combination of parameters was oscillation frequency as 12.5Hz, rotation speed as 120r/min, and chute inclination angle as 20°. Based on the optimized parameters, the results of the bench test showed that under the same high feeding condition, the cleaning loss rate after the configuration of the device was 3.97%, which was 49.8% lower than that of the original cleaning system, and the impurity rate was 3.71%, which was 34.7% lower. The results showed that the optimal cleaning system could meet the requirements of the crawler combine harvester for the low-loss and high-efficiency cleaning operation of high-density and high-yield rape. The research results can provide reference for the design and improvement of cleaning system for oilseed harvesting.