For a long time, the development of green shipping has been highly valued by countries and organizations. Biomass gasification-based green methanol is seen as a long-term alternative to conventional shipping fuel to reduce greenhouse gas emissions in the maritime sector. While the operational benefits of renewable methanol as a marine fuel are well-known, its cost and environmental performance depend largely on the production method. In this study, a green methanol production system based on the integration of biomass gasification and water electrolysis is proposed and evaluated via the parametric and thermodynamic analysis methods. The water electrolysis is used to increase the hydrogen content in syngas, thereby increasing the production of methanol. The results show that as the S/C ratio increases, the mass flow rate and the calorific value of product gas, the mole flow rate of methanol decreases. The enhancement of the H2/CO ratio can increase the mole fraction of H2, thereby increasing the methanol yield. The mole flow rate of methanol dramatically increases from 925.0 kmol/h to 3725.2 kmol/h. Additionally, the mole flow rate of methanol in the proposed system is 10776.0 kmol/h, larger than the traditional system of 3603.4 kmol/h. The carbon element conversion rate of the proposed system is 94.6%, higher than the 31.5% of the traditional system. This system can significantly provide an efficient green methanol production method for the shipping sector, while also helping to find a feasible solution for the consumption of renewable energy.