Overview is given to the synthesize electric propulsion system through the comparison between electric propulsion system and diesel engine propulsion system, as well as the advantages and structure of electric propulsion. General descriptions are offered to key equipments such as high-power frequency converter, propulsion motor, podded propulsion unit, power plant management and monitor system. With the progress of new technologies, the benefits of marine electric propulsion will be highlighted and win a golden era in the 21st century.