Abstract: The influence of belt speed, air pressure and selection number on the rate of mixed gangue and rate of separated gangue was researched by orthogonal experiment method and using separation device with air-blowing method, and the experiment results were analyzed by regression and variance analysis. The analysis results show that the rate of mixed gangue increases with belt speed and decreases with the increase of air pressure and number of selection; rate of separated gangue decreases with the increase of belt speed and increases with the increase of air pressure and number of separation. The belt speed, air pressure and number of separation have a great effect on rate of mixed gangue and rate of separated gangue, the order is belt speed, number of separation and air pressure.