The gasification process is the core of the marine fuel gas supply system, whose simulation research is critical for ensuring the rational design of the gasification system and the safe operation of the fuel gas supply system.The optimization of gasification scheme was carried out based on the high- and low-pressure fuel gas supply system of a large LNG-powered vessel. A method for simulating the gasification process using Aspen HYSYS software under the maximum operating condition was proposed, to verify the rationality of the gasification scheme. And, the gasification process under various typical operating conditions was then simulated and validated. The influence of LNG methane concentration and inlet pressure on the design of the gasification scheme was explored. It was found that the heat duty of the vaporizer increased with LNG methane concentration and decreased with inlet pressure. This provides a theoretical basis for the optimal design of the gasification process in marine fuel gas supply systems and contributes to the safe and stable operation of dual-fuel power systems.