Abstract: In order to improve the cracking performance, this study optimized the operating parameters of key components by analyzing the influence of different operating parameters on the cracking performance for the walnut cracking machine with self-grading extrusion. Through kinematic analysis of walnuts between the roller and the plate, the key factors affecting shell cracking and kernel extraction were determined, which included the cracking angle and roller speed. The combination experiment of two-factor and five-level quadratic orthogonal rotating center was carried out with shell cracking rate, whole kernel rate and energy consumption as the experimental indexes. Data analysis was performed using Design-Expert software to establish regression models between the factors and the test indicators. ANOVA obtained the major and minor factors affecting shell cracking rate, whole kernel rate, and energy consumption. The interaction of the two factors was analyzed using the response surface methodology. The regression model was multi-objectively optimized according to the importance of the optimization objective. The results showed that the optimal combination of working parameters was 0.47° of cracking angle and 108 r/min of roller speed. Under these conditions, it yielded a shell cracking rate of 97.24%, a whole kernel rate of 92.03%, and an energy consumption of 1.88 kJ/kg. The relative error between the validation result and the model prediction was less than 5%. The results of variety adaptation tests showed that the optimal working parameters were appropriate for the three varieties of walnuts, including Wen-185, Xinwen-179, and Zha-343, showing that the shell cracking rate was greater than 96%, the whole kernel rate was greater than 90%, and the energy consumption was less than 2 kJ/kg. The results of this study can provide theoretical references for the improvement and optimization of related shell cracking equipment and the selection of cracking and processing parameters for different varieties of walnut.