In response to a leading vessel design requirement that cooperating DP-3 closed ring power system, this paper introduce an optimize design of a new deep-water diving support vessel of Shanghai Salvage Bureau from the analysis of the thruster configuration, electric load balance and single line diagram, combined with the DP capability assessment. Then, we divide the overall structure and equipment redundancy grouping of the vessel’s closed ring power station on account of “three-engine rooms, four-DP zones” design. Meanwhile, this paper discusses the design of dual feeding power supply for a special separated switchboard and the protection logic during closed ring operation.