Abstract: In a sodium-cooled fast reactor, the steam generator (SG) is one of the key equipments in the secondary loop main cooling system. When the heat transfer tubes break, a sodium-water reaction (SWR) will occur, and large amounts of hydrogen gas, sodium hydroxide and exothermic heat will also generate in the system, which will affect the safe operation of SG seriously. In this paper, the numerical simulation of SWR was carried out by using FLUENT. The analytical results show that the maximum temperature of reaction region can reach 1 564 K when the leak diameter is 0.2 mm. The maximum temperature increases with leakage rate, but keeps in a certain range. These results are consistent with the experimental results in Japan. The leakage rate influences the extension trend of NaOH and H₂. It is confirmed that the present method is practically applicable to the phenomena of SWR. The maximum temperature at any leakage rate and the concentration values of NaOH and H₂ at any position can be obtained. It can provide reliable data for prediction of adjacent tube wastage and failure time in favor of the further SWR accident safety analysis.