Due to the lack of accurate discrete element simulation model parameters in the design optimization process of key agricultural machinery components under conservation tillage in black soil area, the optimization improvement of the machinery and tools is restricted to a certain extent. In order to obtain the accurate discrete element simulation contact parameters of the corn straw-soil mixture in the black soil area, the discrete element simulation model of the corn straw-soil mixture was constructed. The physical test and the EDEM simulation test were combined and the Hertz-Mindlin with JKR contact model was used for discrete simulation contact parameter calibration. Using the Plackett-Burman test in the DesignExpert software, the parameters that had a significant impact on the repose angle were selected as follows: soil-soil rolling friction coefficient, soil-steel static friction coefficient, straw-soil rolling friction coefficient, soil JKR surface energy; and the optimal value range of the four parameters were further determined through the steepest climbing test. According to the Box-Behnken test principle, the repose angle was used as the response value to establish a quadratic regression model between the repose angle and the significant parameters; the actual repose angle was used as the target, and the software was used to optimize. The function optimized the significant parameters and the optimal parameter combination was obtained as follows: straw-soil rolling friction coefficient was 0.16, soil-soil rolling friction coefficient was 0.24, soil-steel static friction coefficient was 0.75, and soil JKR surface energy was 0.67J/m2. The optimal parameter combination was compared and verified through simulation experiments, and the relative error between the simulated repose angle and the physical test repose angle was 1.64%. The research results showed that the calibrated parameters were true and reliable, which can provide a theoretical reference for the discrete element simulation of the corn straw-soil mixture in the black soil area.