Abstract: As the lifeblood of global trade,the international shipping industry accounts for approximately 3% of global carbon emissions,posing a significant challenge to the achievement of climate targets. Onboard carbon capture and storage（OCCS） technology is widely regarded as an important pathway for the shipping industry to move toward net-zero emissions because of its substantial emission-reduction potential and compatibility with existing vessels. This study focuses on the economic feasibility of OCCS technology and systematically analyzes its cost structure. The results reveal that initial capital expenditure and the additional fuel consumption caused by the capture system are the major economic barriers limiting its large-scale adoption. A quantitative case study of a medium-range（MR） tanker shows that,under specific operating and market conditions,the investment payback period of the OCCS system is 8. 38 years,preliminarily demonstrating the economic potential of this technology for commercial application. Furthermore,the sensitivity analysis indicates that the carbon tax rate and the CO₂ market price are the decisive variables affecting the payback period,as well as key uncertainties that should be emphasized in future techno-economic assessments. Based on these findings,this study suggests that the commercialization of OCCS cannot rely solely on technological maturity,but requires a coordinated support framework integrating policy guidance,technological innovation,and market mechanisms. By providing empirical data,this study offers an analytical basis for translating the shipping industry's macro-level decarbonization strategy into micro-level economic decision-making and helps fill the gap in quantitative assessments of OCCS applications for specific ship types.