Abstract: Aiming at the problems of high impurity content in the membrane after sieving the membrane impurity mixture caused by the lack of theoretical support of the trommel screen type membrane and impurity separation device and the unreasonable setting of working parameters. The dynamic distribution of the air flow field in the sorting chamber of the trommel screen type membrane and impurity separation device and the movement of materials in the device are numerically simulated to determine the best combination of working parameters, by using computational fluid dynamics and discrete element coupling method. The airflow angle, air inlet wind speed and trommel screen speed were selected as test factors to conduct gas-solid two-phase flow coupling simulation test, to analyze the influence of various test factors on the air flow field in the sorting chamber and the movement of materials in the device. Taking the film content rate of the output, the film content rate of impurities and the output of residual film as evaluation indicators, a three-factor, three-level orthogonal test was carried out. The test results were subjected to multiple regression analysis, and the best combination of working parameters was obtained through the multi-objective optimization method: the air inlet wind speed was 8.5 m/s, the airflow angle was 8°, and the trommel speed was 26 r/min. The verification tests were carried out under these conditions, the results showed that the film content rate of the output was 89.31%, the film content rate of impurities was 1.99%, and the output of residual film was 0.032 6 kg/s. The relative error between the experimental results and the theoretical optimization value was less than 7%, and the indicators were 0.87, 3.82 and 6.57 percentage points better than that before the optimization of working parameters, respectively. The study verified the feasibility of analyzing the flow field of the trommel screen type membrane and impurity separation device based on DEM-CFD gas-solid two-phase flow coupling simulation, and provided a theoretical basis for the optimization of the operating parameters of the trommel screen type membrane and impurity separation device.