The problem of environmental pollution has extended beyond the domestic level to the international level. Accordingly, to regulate environmental pollution, the International Maritime Organization (IMO) strictly regulates air pollutants. Among them, the amount of air pollutants emitted from ships is considerable, and the regulations are being strengthened. In order to protect the air environment, IMO is gradually increasing the limit of the exhaust gas emission of ships and is in the process of achieving the target value. In order to satisfy these strict regulations, many fields are making ceaseless efforts to reduce exhaust gas emissions. For example, In the field of ships, in order to use fuel efficiently, ships are sailing at an economical operating speed. However, these efforts alone are insufficient to achieve great results in reducing exhaust gas emissions, Therefore, there is a demand for the introduction of eco-friendly ships, and research and development on various propulsion system technologies are in progress. Among them, there is an electric propulsion system, which is an eco-friendly propulsion system. In order to use the electric propulsion system, a battery is required, but the current technology has the disadvantage of being bulky and has a space limitation when installing it in a small vessel. Therefore, in this paper, the diesel-electric hybrid propulsion system is used to avoid the low-load operation of the engine in this section by using the electric propulsion system possible in the low-load section where the fuel efficiency is the worst in the diesel propulsion system and generates a lot of exhaust gas. In the middle load to high load section, the diesel engine can achieve optimum control by using the equivalent consumption minimization strategy to achieve optimum efficiency. As target vessels to which this is applied, a 39ton general passenger ship, a 99ton car ferry, and a 106ton car ferry were selected. The fuel consumption and exhaust gas emissions of conventional diesel propulsion ships and diesel-electric hybrid propulsion ships were compared and analyzed through simulations based on the load operating environment of ships operating in real sea areas.