Basalt-CO2 mineralization sequestration is an emerging CCUS (Carbon Capture, Utilization, and Storage) technology for achieving China's ‘dual carbon’ strategy, among which the accurate evaluation of the sequestration potential of basalt formations is a key technical indicator for measuring the feasibility of mineralization sequestration projects. Currently, there are various methods for calculating the mineralization sequestration potential of basalt, such as the mineral replacement method and the unit mineralization method, but there is still a lack of consensus in the industry regarding the calculation principles, accuracy, and applicable conditions of different methods. Based on the independently developed CO2 steady-state seepage test system, this study conducted injectability mineralization tests to investigate the dynamic change processes of indicators such as solution ion concentration, permeability, and secondary mineral growth quality of basalt samples with different pore and fracture characteristics in the Wenchang area of Hainan during the long-term mineralization sequestration process, and by comparing the calculated values, the error ranges and principles of various calculation methods were clarified; on this basis, an optimized calculation method for carbon sequestration capacity was proposed and applied to calculate the carbon sequestration capacity of basalt formations in Heishanling (HSL), Penglai Town, Wenchang City, Hainan, and Bailonggang-Sanjia Port Area (SJG), Shanghai. The results show that: mineral dissolution mainly occurs in the early stage of the mineralization reaction, the concentrations of Ca2+ and Mg2+ ions are in a supersaturated state, and the permeability increases slightly followed by a continuous decrease; the growth of secondary minerals shows obvious regional characteristics, with dissolution reactions dominating in the inlet section and precipitation dominating in the outlet section, and simultaneously, affected by the pressure dissolution effect, the opening of fractured basalt decreased by 5.23 % and 2.97 % respectively during the mineralization process, the mass percentage of C element on the surface of intact basalt after the reaction was 2.6 %, and the reduction in fracture opening and pore 'blockage' are the main reasons for the decrease in permeability; differences in pore/fracture structures directly affect the carbon sequestration potential of basalt, and the carbon sequestration potential of basalt with large pores and fractures is 135.7 % higher than that of intact basalt with small pores; a comparison between the theoretical calculated values and experimental values of basalt carbon sequestration potential shows that the calculation error of the mineral replacement method is the lowest at 2.4 %, while the calculation results of the unit mineralization method and the pore filling method are significantly overestimated, and the optimized calculation method for carbon sequestration potential can improve calculation accuracy without introducing additional empirical parameters; using the optimized method, the potential carbon sequestration capacities of the proven basalt formations at the two sites (HSL and SJG) were calculated to be 7.01×104 tons and 9.50×104 tons under the condition of a 7500 m2 site, respectively. The above research results can provide a basis for the feasibility analysis of subsequent mineralization sequestration projects.