Reducing CO 2 emissions in the international shipping industry is crucial for mitigating global warming. International Maritime Organization (IMO) has set a decarbonization target of reducing CO 2 emissions in the international shipping industry by at least 70% compared to the 2008 level by 2040. Ship-based carbon capture (SBCC) is an effective technology for reducing CO 2 emissions from ocean-going ships. The core of SBCC is efficient and low-cost absorption solutions. In this paper, based on the exhaust emission characteristics of ocean-going ships, the seawater− sodium hydroxide method for decarbonization in ocean-going ships is developed for the first time. First, the decarbonization performance of the seawater−sodium hydroxide absorption solution is investigated, including the influence of NaOH concentration, absorption solution flow rate, and CO 2 volume concentration on the decarbonization process. The results show that the seawater−sodium hydroxide absorption solution can efficiently capture CO 2 from ship exhaust. For the ship exhaust with 9 vol % CO 2 , when the absorption solution flow rate is 0.75 L/h, the decarbonization rate reaches 51.80% using the seawater−sodium hydroxide absorption solution with 1.5 mol/L NaOH. When the NaOH concentration increases to 2.5 mol/L, the decarbonization rate increases to 83.38%. Furthermore, TiO 2 nanoparticles are added to the absorption solution to investigate optimization schemes for decarbonization of the seawater−sodium hydroxide solution. The influence of nanoparticle mass concentration and size on decarbonization is studied, and the optimization parameters of the seawater−sodium hydroxide method are obtained. With 0.09 wt % of 30 nm TiO 2 in seawater−sodium hydroxide absorption solution with 1.5 mol/L NaOH, the maximum enhancement factor (E) is 1.78, achieving the maximum decarbonization rate of 92.35% for ship exhaust containing 9 vol % CO 2 . The seawater−sodium hydroxide method is a feasible and cost-effective method to reduce CO 2 emissions in ocean-going ships. The experimental results provide a valuable reference for the application of the seawater−sodium hydroxide method in ocean-going ship decarbonization and lay an important foundation for further research on SBCC technology.