Partial discharge (PD) monitoring is an important way to find the insulation defects of power equipment and maintain the safe operation of power grid. Based on the advantages of Distributed Feedback (DFB) laser, such as narrow line width, low noise and long coherence length, a vibration sensing system for partial discharge monitoring was designed and used to detect PD in this paper. The DFB laser glued on the cantilever beam was used as the sensing head, the wavelength change of DFB laser was converted into the output intensity change of the interferometer by using the fiber Michelson interferometer, and the Phase Generated Carrier (PGC) algorithm was used to demodulate partial discharge signals. Cantilever was designed and vibration characteristics was simulated, and its first order resonant frequency is 876Hz. The relationship between the arm length difference of Michelson interferometer and the system sensitivity was studied. The pulse igniter was used as the partial discharge source for discharge detection, which verifies the feasibility of the system for partial discharge detection. The results show that the system can detect the discharge signal of 800 ~ 900Hz with the sensitivity of -74.67dB re rad/Pa.