The liquid ammonia pressurized supply and ammonia capture are carried out based on the demand of ship main engine powered by ammonia fuel. The current study firstly sets up a three-stage pressurized supply mode with a buffer tank, and then analyzes and simulates the key points such as the form of fuel tank, stepped pressurization, elimination of pipeline gas resistance, inerting explosion prevention and ammonia emission capture. The simulation results show that the backflow pressure of the fuel is within the preset range, and this design can achieve stable supply to the main engine after pressurization and temperature increase, and can achieve the effective capture and process of ammonia emissions. The system analysis shows that it is feasible and stable to adopt the semi-cooled and semi-pressurized fuel tank, combined with a two-stage pump and a buffer tank, forming a three-stage pressurization system. The use of water mist spraying combined with adsorbers can effectively capture the ammonia and control ammonia emissions within 22.8 mg/m ³.