Abstract：The early Repetitive Shock (RS) machine has some inherent flaws, such as energy uniformity in frequency domain, lower energy below 2KHz, and so on. These characters confine the application of RS machine in the Reliability Enhancement Testing of electronic assemblies. However, many key technologies of RS machine have not been studied in detail in our country because of lacking technology stuff. In this paper, vibrators which are crucial components of RS machine are regarded as the specific objects. Based on the generating mechanism of exciting signals produced by vibrators, the analysis formulas of power spectrum density and low frequency energy of exciting signals are concluded respectively, the relationships between the parameters of vibrators and the low frequency energy of exiting signals produced by vibrators are studied deeply, and the effective approach to improve the low frequency energy of vibration signal produced by RS machine is put forward at last. In a word, the results of this paper are useful not only to the optimization design but also to the self exploiture of RS machine.