The modeling and active vibration control of a piezoelectric flexible manipulator system are presented， taking the Euler-Bernoulli cantilever as an example. Considering the non-linearity and complexity of a flexible system， the transfer function combining the input voltage of the actuator and the output voltage of the sensor arises from the experimental identification. Aiming at the elastic vibration， the weighted matrix of the model based on the linear quadratic regular （LQR） theory， which is difficult to solve， is optimizaed by the genetic algorithm. On this basis， the experimental platform is construacted and the control program is compiled for the vibration control test of a flexible manipulator. The results show that the proposed method suppresses the vibration of the flexible manipulator both under free attenuation and continuous excitation as demanded.