Abstract: The simulation of sodium-water reaction accident is the difficulty in the development of the simulating system of sodium cooled reactor. In order to solve this problem, a simulation program of sodium-water reaction accident was designed based on the mathematical physical equation of sodium-water reaction accident caused by water leakage in heat transfer tube of sodium-cooled fast reactor steam generator. Based on SimTherm thermal-hydraulic simulation program and the structure of sodium-cooled fast reactor, a second-circuit model of sodium-cooled fast reactor was designed for the study of sodium-water reaction accidents. By coupling the simulation program of sodium-water reaction accident with SimTherm, the simulation of sodium-water reaction accident was realized, which provides a new idea for the development of sodium-cooled fast reactor simulator.