A high sensitivity micro-vibration senor based on distributed Bragg reflector (DBR) fiber laser is designed and demonstrated. The sensor structure uses common mass-spring system. Due to gravity, the DBR laser cavity is subjected to lateral pressure caused by the mass. Because the lateral pressure that the laser cavity suffers changes when the testing platform is vibrating, the beat frequency generated by two orthogonally polarized modes of the laser output changes. By the high-speed photodetector and multi-channel data acquisition platform, the beat frequency signal is collected. The signal can be dealed with through the LabVIEW programming and the real-time monitoring of the vibration acceleration signal is achieved. Theoretical analysis and experimental results show that, the sensor has a very high acceleration sensitivity, which is up to gigahertz for an acceleration of gravity g, and can detect very weak vibration signal. Compared with the traditional optical fiber vibration sensors, this sensor convert optical spectrum analysis to frequency spectrum analysis, which makes the signal acquisition and demodulation easier, and obtains a higher sensitivity. Further analysis shows that the measurement of this structure in the micro-gravity environment is also feasible. Therefore, it has great potential in the micro-vibration measurements of key components of aerospace craft.