Abstract: In order to solve the question of vent impurity of the sugarcane combine harvester, the new fan on the vent impurity device of sugarcane harvester was designed, and experiments were carried out on the test-bed. The wind speed of outlet of impurity discharging fan was guide line, the single experiments were conducted to study in the following factors: the new fan speed, inlet mode and inlet area. The results show that the best parameters of impurity discharging fan were respectively speed of fan was 1800r/min, inlet mode was the axial, inlet area were 16475, 19119mm2 and distance of fan outlet was 50mm. The wind speed averages of the five measurement points were respectively 13.867, 14, 11.633, 11.333, 12.383m/s. In the optimal parameters were proved to be the best by experiment on the impurity discharging fan.