Abstract: Aiming at the multiple working conditions of steering knuckle arms in mining dump truck steering systems during operation, this paper established a load mathematical model and obtained the dangerous load working conditions. In consideration with primary and secondary relations among these working conditions, an optimization design model of steering knuckle arms under multiple working conditions was elicited after the weight of each working condition was valued by fuzzy evaluation as well as the objective function and constraint function were response surface modeled by response surface method. Then Matlab software was used to program and solve the design model, and finally optimization design of steering knuckle arms under multiple working conditions was realized. The rationality of practical application and the value of optimization under multiple working conditions were further confirmed in comparison with the optimal results under a single working condition.