Since low-frequency line-spectrum vibration exists in ship mechanical equipment，an electromagnetic-hydraulic activepassive vibration isolator is designed with an electromagnetic actuator and a hydraulic suspension structure. The composite vibration isolator uses the output force of an electromagnetic actuator to suppress low-frequency line-spectrum vibration. The hydraulic suspension structure isolates broadband vibration and enlarges the electromagnetic force. It has the advantages of small footprint，large carrying capacity，and large output force. The electromagnetic part and hydraulic suspension part of the composite vibration isolator are modeled and analyzed，respectively. A distributed multi-channel modified decoupling algorithm is proposed by considering the channel coupling vibration to ensure the convergence of filter weight coefficients. A multi-channel active-passive vibration isolation control experiment with multi-line spectrum excitation has been carried out. The results show that the active-passive composite vibration isolator can achieve an average attenuation of 35.12，39.51 and 38.35 dB on three line spectra，and the control effect is significant.