With the rapid developments of DC microgrid technologies and the demands of marine sustainable energy utilizations, the onboard DC microgrid becomes a new research focus. The control and Power Management Strategies (PMS) of a marine DC microgrid are two vital issues to maintain the stability, safety and efficiency of a shipboard power system. To deal with the power management problem, this paper firstly designs an onboard DC microgrid and then focus on the power management strategy design; afterwards, the onboard DC microgrid and the PMS are simulated with Matlab/Simulink, and the simulation results finally show the efficiency of the proposed method.