In the present study, a numerical methodology for sodium combustion has been developed for the safety evaluation of a liquid-metal-cooled fast reactor. The methodology includes a fast-running zone model computer program for safety evaluation, a field model program for multidimensional thermal hydraulics, and a chemical reaction analysis program based on chemical equilibrium theory. Two recently performed experiments have been analyzed using the computer programs, and the numerical results are in good agreement with the experiments. Although sodium combustion is a complex phenomenon, use of these computer programs gives better understanding of the coupled thermal hydraulics and chemical reaction.