Abstract: A new spherical model with cones on the sodium droplet surface was applied to replace the traditional and spherical model in the spray fire calculation of sodium cooled fast reactor, which could improve the accuracy of simulation based on the actual combustion phenomena. Based on the different mechanisms of the surface oxidation, pre-combustion and combustion stages, the mathematical models were established and combustion temperature characteristics were simulated under different initial temperatures (200-500 ℃) of sodium droplet and oxygen fractions (4%-20%) by introducing the proportion factor γ of the mass participating in the oxidation reaction to vaporization in the unit time. The simulation results are well consistent with the experiment data, and the variation rule of γ values was analyzed.