In this paper, calculation method for heat of detonation of industrial explosive containing C?H?O?N?Na?K?Ca?Cl is described. Calculating formula for this type of explosive's oxygen balance value is given. Equations of explosive reaction in varying oxygen balance values and element numbers are discussed. On the basis of manual deduction ,a computer program is made and computer deduction for the relation expression of heat of detonation with formulation for mixed explosive is achieved.