In this paper, the electromagnetic propulsion system using high frequency AC is proposed to solve several problems which are caused by electrolysis of sea water. And ZCS (Zero Current Switching) high frequency inverter is proposed as a high frequency power supply applied for this system. Moreover the operating method of the proposed power supply is presented as a method of controlling speed of an electromagnetic propulsion system. Especially, it is proved that electrolysis of sea water is suppressed and that poisonous gas is not generated, through the experiment.