Abstract: <SPAN lang=EN-US>Process of producing sodium chlorate by electrolyzing sodium chloride will generate redundant disproportionation heat.The quantity of disproportionation heat relates to the design of heat exchanger to move away this part of heat and it also relates to the estimated value of developing this part of heat.But calculation of energy balance in electrolysis reaction is very complicated because it contains imported electric energy,critical heat (water evaporation),and pyrometric effect of chemical reaction.So it is difficult to find out the calculation method for this kind of electrolysis reaction in general chemical desgin books.The theoretical and practical calculation methods for disproportionation heat were discussed.Simple and reasonable methods,which had small difference in calculation results were given out.Then the methods were testified by the existing production data.At last, the conclusion that 30%~35% electric energy of electrolysis converted to utilizable disproportionation heat and the disproportionation heat was 5.55</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman"">×</SPAN><SPAN lang=EN-US>10</SPAN><SPAN lang=EN-US><SUP>6</SUP>~6.34</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman"">×</SPAN><SPAN lang=EN-US>10</SPAN><SPAN lang=EN-US><SUP>6</SUP> kJ/t calculated according to sodium chlorate output had been obtained by combining the calculation results and the existing production data.The data is reliable enough for designers to use.<BR></SPAN>