To solve the problem of power distribution in unmanned diesel-electrical power system，this paper proposes an improved constant power control strategy of inverter.The active power control command of the strategy is obtained by calculating the frequency deviation and droop coefficient，and its reactive power control command is obtained by calculating the voltage deviation and droop coefficient.The control strategy can be used to directly introduce the dynamic changes in the frequency and voltage of diesel-engine generator into the inverter control，equally distribute the power to the inverter and diesel-engine generator when operating in parallel by properly setting the droop coefficients，and deal with the generator overload or reverse power caused by sudden loading or unloading in unmanned systems.Simulation and experiment verify that the proposed control strategy is feasible and effective.