Abstract: The application of large engineering ship in marine engineering field is more and more extensive. But the energy saving problem of large power systems in large engineering ships is becoming increasingly prominent. Closed-ring running model in power system is a new design concept for energy saving and consumption reduction, and the reliability of the system is guaranteed. We introduce the advantages and disadvantages of closed-ring power system in detail. Several problems in the design stage when the closed-ring power system is applied to large engineering ship are also pointed out.