In order to improve the sand collection efficiency of the wind erosion instrument and accurately grasp the sand movement law, the influence of structural parameters of the wind sand separator inside wind erosion instrument on the sand collection efficiency was analyzed by using computational fluid dynamics (CFD) simulation method and combined with the wind tunnel test. The wind-sand separator model was established in Fluent platform, numerical analysis was carried out based on RNG k-εmodel, and the discrete phase model (DPM) method was used to calculate the sand collection efficiency and complete the simulation of the related particle dynamics inside the wind erosion instrument. The wind erosion meter was improved from wedge shape to cylindrical shape, which optimized the structure of the wind erosion meter and improved the sand collection efficiency. The effects of the inlet wind speed of inlet pipe, the particle size of sand particles and structural parameters of wind-sand separator (length of the inlet pipe, depth of the exhaust pipe insertion, cone angle of the conical deflector plate, and the length of the cylinder) on the sand-collecting efficiency were investigated. The simulation results showed that when the wind speed was 13.8m/s, the particle size less than 0.01mm was the main particle that affected the sand collection efficiency. The structural parameters of the wind-sand separator were subjected to a single-factor test, the level range of the test factors was preferred, and the Box-Behnken test was carried out to optimize the values of the parameters to obtain the optimal parameter combinations: the length of the inlet pipe was 12mm, the depth of the exhaust pipe insertion was 70mm, the cone angle of the conical deflector plate was 40°, the length of the cylinder was 160mm, and the sand-collecting efficiency was 77.05%. According to the optimal parameter combination, the wind erosion instrument model was processed and wind tunnel test was carried out, and the sand collection efficiency was 74.38%, and the error with the simulation results was 3.47%, which was better than the common wedge-shaped wind sand separator with better sand collection effect.