Aimed at a special testing requirement for fatigue life of sensitive components, such as diaphragm, a new fatigue life testing system based on the exciter and digital waveform synthesis techniques is designed. The key technologies of frequency control and amplitude control in fatigue test are researched by analyzing the frequency and the amplitude accuracy, and experimental studies are carried out. Experimental and analytical results show that the test system has characteristics of high resolution, high accuracy, low cost, low power consumption, long-term use, thus the result is stable and reliable. The system can meet the special requirement of long-term test.