The medium and high frequency vibration caused by the meshing of the gear in the helicopter's main reducer is one of the main sources of noise in the helicopter cabin. The vibration transmitted to the body can be suppressed effectively by designing a reducer strut with vibration isolation performance， and then the cabin noise induced by gear meshing can be reduced. In this paper，based on the piezoelectric stack/rubber periodic structure， a kind of smart periodic strut for active/passive hybrid vibration control is proposed for helicopter cabin noise reduction. It not only meets the requirements of strength and stiffness， but also has excellent multi-frequency and broadband damping capacity. The piezoelectric stack and the rubber material are arranged periodically to form a periodic structure， which has the characteristic of "mechanical filter" in a specific frequency range. At the same time， by adjusting the driving voltage and current of the piezoelectric stack and changing the dynamic stiffness of the piezoelectric stack， the function of active vibration reduction can be realized. In order to analyze the performance of active/passive hybrid vibration control of smart periodic strut， the electromechanical coupling dynamics model of smart periodic strut based on transfer matrix is established， and the correctness of the model is verified by multi-physical field simulation software. Based on this model， the optimal vibration isolation performance of smart periodic strut with limited driving voltage and current is analyzed. Under the condition that one end of the smart periodic strut is fixed， one end is subjected to 10N excitation force， the maximum driving voltage is 20V， and the maximum driving current is 1A， the smart periodic strut has the ability to completely attenuate the vibration above 692Hz， and can control the vibration below 692Hz to a certain extent. In addition， the influence of material and mechanical boundary conditions on active control is also studied， especially the influence of damping and excitation force of rubber material on driving voltage and current required for active control. The strength and stiffness of the smart periodic strut are verified by the finite element model， and the engineering feasibility of the intelligent periodic struts proposed in this paper is verified. A piezoelectric stack periodic strut with 3 cells is composed of the piezoelectric stack actuator and the PVC strut as a simplified model of the smart periodic strut. The control performance of active and passive hybrid vibration control， the influence of mechanical boundary conditions on vibration isolation performance， and the relationship between the driving voltage and current and optimal driving voltage and current are analyzed.