The invention comprises three phase four wire system ship power grid power management system and method which comprises a three phase four wire system grid, a generator, a main control cell, a plurality of generator set control units connected with the main control cell and a load control unit connected between the main control cell and the power grid, the local control unit connected with a single-phase load, the power grid which supplies power to the single-phase load by taking the phase of U/v/w to connect with neutral wires, the main control cell and the power grid and the generator set control unit and the generator are connected with the current transformer and the voltage transformer respectively, the main control unit is connected with human-computer interface. The invention also discloses management method; the real-time power of the ship equipment and equipment power is adjusted dynamically by automatic intelligent devices, the distribution of three-phase load can be within the threshold rang of the stability requirement of the ship power grid., when the balance occurs the lode is cut, thus the safe use of the ship can be guaranteed.