Based on waveform spring, a preload method for angular contact bearing of space actuator is presented. Design for this spring, stiffness tests of room temperature, low-high temperature and after compression resistance are introduced. By the test results, stability of its stiffness is verified. Then, the waveform spring is fixed in the space actuator, and at the same time, the preload of waveform spring on the bearing can be controlled and measured by a pressure sensor. Feasibility, stability for the preload of waveform spring on the bearing and engineering value of this method are proved by low-high temperature test.