The marine electric propulsion system has the advantages of small volume, lightweight, flexible layout of the engine room, high automation and high comprehensive utilization rate of the power grid, so that more and more marine engineering vessels have adopted the AC electric propulsion system. This dissertation introduces the advantages and components of the current AC ship vessel propulsion system, and some problems, which should be noticed in the design of the whole system, are mainly discussed. © 2016, Editorial Office of Ship Building of China. All right reserved.