The integration and unification of components have driven a sharp increase in the demand for large machine tools. High-speed and high-power electric spindles for CNC machine tools can achieve processing within a wide speed regulation range, thus becoming a research hotspot. In response to the poor compatibility and insufficient fault tolerance of traditional test benches, a new type of high-speed electric spindle test platform is designed. Aiming at the fact that the conventional electric spindle structure cannot compensate for the radial external load in real time, an optimized design scheme for the electric spindle structure is proposed. Since the traditional loading methods cannot be coupled and applied according to the actual situation, a new method for simulating the alternating load coupling situation of the electric spindle is proposed. Finally, three different types of electric spindles are selected for testing. After long-term verification, the designed test platform has stable performance. Through the optimization of the electric spindle structure, the simulated load can be better applied. The method proposed in this paper has important engineering practical value.