The half-shaft spline is a crucial component of the vehicle’s drivetrain assembly, especially the electric vehicles (EVs) with starting torque. This study aims to perform fatigue life testing and optimization analysis on the existing half-shaft splines. Through load spectrum testing, fatigue life experiments, and simulation analysis, fatigue life simulation calculations are conducted on the existing half-shaft splines, by comparing the obtained results, it is possible to validate the accuracy of the finite element model and the effectiveness of fatigue damage accumulation theory; After conducting the validated comparative analysis, an optimization analysis of the fatigue life can be carried out by adjusting relevant parameters, such as module and pressure angle. This optimization process aims to enhance the fatigue performance of the half-shaft splines. The results demonstrate that the optimization process leads to a significant improvement in the performance of the half-shaft splines. Specifically, the analysis shows a remarkable 20% decrease in the overall stress levels and an impressive 154% increase in the overall fatigue life of the splines. During the subsequent vehicle integration process, this method offers a relevant theoretical foundation for effectively improving the fatigue strength of key components.