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To reduce the loss of maize and ensure certain cleanliness of maize after screening operations, the movement of maize mixture was analyzed in the airflow field, and the stepped screen body was designed based on shell screen. The stepped buffer zone was designed by analyzing the theory of maize’s collision to temporarily retain grains in the stepper and reduce the effect on carrying maize from maize mixture and avoid maize accumulation in the ladder. However, maize debris directly went across the ladder. To make the screen amplitude as 19mm, the computational fluid dynamics and discrete element method (CFD-DEM) were coupled in the quadratic orthogonal rotational-combinational simulation tests. The factors were the inlet velocity and direction angle of airflow, height of the ladder and vibration frequency of screen. The indexes were the loss and cleanliness of maize grains collected. The test data were analyzed by the response surface method and the regression mathematical models were multi-objective optimized by using Design-Expert software. The results showed that the loss and cleanliness of maize were 1.69% and 98.8%, respectively, when the inlet velocity of airflow was 16m/s, the direction angle of airflow was 25°, the height of the ladder was 8.36mm, and the vibration frequency of screen was 4.45Hz. The performances met the requirements of corn harvest. The performance tests were done in the laboratory to verify the accuracy of the simulation results. The rate of maize loss was 2.12% and the cleanliness of maize grains collected was 99.16% after screening. Compared with the flat shell screen, the loss of maize grains across the stepped shell screen was reduced by 1.14 percentage points and the cleanliness of maize grains was increased by 1.98 percentage points. The cleaning performance of screen was improved.