The simulation of separation channel airflow field distribution was implemented with FLUENT software. The CFD-DEM coupling method was used to simulate the separation progress of the mixtures in the separation channel. For fluid outlet velocity, inclination angel of inlet tube and inclination angle of separating channel factors was carried out by simulation experiment, determine the optimal technological parameter of separating channel as follows: inclination angel of inlet tube was 60°, inclination angle of separating channel was 35°, fluid outlet velocity was 7.881 m/s, and the results were the same with the physical prototype. The feasibility to use CFD-DEM coupling method to study the separation device for lotus seed and its contaminates was verified. The result of this study can be taken reference for the research on separating equipment for lotus seed kernel and shell.