Aiming at the problem that the gain amplitude is hard to identify in advance and the gain value can not be set properly, an auto gain control (AGC) strategy using Kalman filter is presented to deal with the uncertainty in vibration acquire system. The design principles, algorithms and circuit implementation are described. The experimental results show that this method can not only control auto gain in dynamic data acquiring system, but also get wide gain amplitude range without setting the initial value. It has important practical application value in high dynamic range data acquisition.