在电火工品一维热传导方程的基础上 ,给出了电火工品热传导方程 ,并用变分法推导了电火工品临界参数值的计算公式 .通过对药剂 HMX,PENT,RDX的计算表明 ,临界点火条件和临界点火温度随药剂活化能的增大而减小 ,随桥丝输入能量的增大而增大 ,临界点火时间则随桥丝能量的增大急速减小 . On the basis of the one-dimensional heat conduction equation of electro-thermal products, the heat conduction equation of e-pyrolysis products is given, and the formulas for calculating the critical parameters of electro-explosive products are deduced by the variational method.Through the calculation of HMX, PENT and RDX It shows that the critical ignition temperature and the critical ignition temperature decrease with the increase of the activation energy, and increase with the input energy of the bridge wire. The critical ignition time decreases rapidly with the increase of bridge wire energy.