Abstract: In this paper, a vibration monitoring system with adjustable gain function is designed. Firstly, the whole framework of the vibration monitoring system is proposed from two aspects of the monitoring layer and the measuring layer. Then the design method of hardware system and software system and the code of software implementation are given. A set of data acquisition devices which can adjust the gain according to the magnitude of the acquisition signal is integrated into the monitoring system by using the control chip and the adjustable gain amplifier. The analog signal generator is used to compare and analyze the signals without gain and with adjustable gain, and the vibration signal is collected under the actual condition of steam turbine generator set. The results show that the vibration monitoring system with adjustable gain function can effectively improve the signal-to-noise ratio of the acquisition signal and the vibration monitoring capability of the turbine generator set.