Abstract: Mining seafloor massive sulfide (SMS) deposits has been increasingly concerned by the geological society. However, the global resource potential remains unclear to the present. Based on the data of Global Database of Seafloor Hydrothermal Systems, we make a global estimate of resource potential for the SMS according to the 3-part mineral assessment practice provided by the U.S. Geological Survey. Firstly, the distribution of SMS deposits is examined, and mid-ocean ridges, volcanic arcs, and back-arc spreading centers are selected as the permissive areas for discovery of new deposits. Secondly, the available SMS deposit tonnage and grade model are chosen to calculate the average resource potential. Thirdly, the number of high-temperature hydrothermal vent and SMS deposits was estimated according to the data of mass flux,heat flux, hydrothermal plume and control areas. The results reveal that the number of SMS deposits is about 1 000, and the total resource potential is estimated to be 6×10⁸ tons, containing about 3×10⁷ tons of copper, zinc and lead.