Abstract: The optimal location and size of the piezoelectric actuators in vibration control of smart beams are optimized.The basic equations of the piezoelectric smart beams are derived.According to these equations,a practical and simple criteria to find the optimal location ,size and even the number of the piezoelectric actuator patches is given.The criterion is independent of the initial condition of the vibration and the control gains.The simulation results show that the control energy can be decreased greatly by using the optimized actuators to control the vibration of smart beams.Moreover,inorder to demonstrate the effectiveness of the vibration control,the vibration control of the flexible beam using piezoelectric ceramic patches is experimented and good control results are obtained with the optimal placed actuator patches.