To reduce ship fuel consumption， an optimized rule-based energy management strategy is proposed to improve the energy efficiency of diesel-electric hybrid power system. The model of the diesel-electric hybrid power system is established based on reverse energy flow， and a rule-based energy management strategy is designed. With the goal of minimizing fuel consumption， a genetic algorithm is employed to optimize the threshold parameters of the rule-based strategy. Case study results of a small polar cruise ship on an Antarctic route show that the proposed method reduces fuel consumption by 3.13% compared to the non-optimized energy management strategy. By appropriately setting the threshold parameters in the rule-based energy management strategy， the fuel consumption of diesel engines can be effectively controlled. The reduction in fuel consumption is achieved by enhancing the battery's ability to “peaks shaving and valley filling”.