To achieve the purpose of dynamic reactive power compensation for piezoelectric actuator, a newproject of passive controllable reactor based on transformer is proposed in this paper. According to the port’s equivalent impedance equations of the transformer’s Ttype equivalent circuit, the equivalent parallel inductance of the transformer will change when the load impedance alters. Therefore, the equivalent impedance of primary winding of the transformer is adjustable. The transformer’s equivalent parallel resistance is enlarged by increasing the inductance of the primary winding and secondary winding.Thus the loss of controllable reactor decreases. The validity of the project is proved by the theory and experiment results.