The invention discloses an energy management system of offshore grid, comprising an information layer, a station control layer and a spacing layer, wherein the information layer, the station control layer and the spacing layer are respectively arranged in a central control station and the platform workstations of a plurality of offshore platform power stations distributed in a sea area; the station control layer is connected and communicated with the information layer and the spacing layer through a communication network; the system carries out the monitoring and control of each generator set, the monitoring and control of each breaker, the distribution, adjustment and control of the reactive power and reactive power contribution, the control of the preferential trip, the management and control of the loop start of a motor, and the cooperative control of the black start of the grid and a platform shutdown system through the information layer, the station control layer and the spacing layer. The invention has the characteristics of high channel speed and degree of automation, highly integrated function, safe and reliable work, easy maintenance, and flexible configuration.