The invention discloses a powder calculation method of heating parts in a sodium-sulfur battery heat preservation box. The method comprises the steps of: 1) heating power estimated value calculation; estimating the estimated values of heating powers of all heating parts in the sodium-sulfur battery heat preservation box; 2) wire connection: connecting the heating parts in the sodium-sulfur battery heat preservation box to corresponding current sensors, and connecting the current sensors to a data collection system having a data recording function; 3) simulative temperature increasing: increasing the temperature of the sodium-sulfur battery heat preservation box according to a preset temperature increasing curve, wherein the data collection system records current change curves of the heating parts through the current sensors; 4) power ratio calculation of the heating parts; 5) determination of rated heating power of a heating part with the lowest heating power; and 6) determination of the rated heating power of other heating parts and a step of control and connection. The method, through accurate calculation on the rated heating power of all heating parts and reasonable arrangement, solves a problem of temperature uniformity, thereby reducing cost and reducing failure points.