A method for estimating critical temperatures (T-b) of thermal explosion for energetic materials is derived from Semenov’s thermal explosion theory and the non-isothermal kinetic equation d alpha/dt = Af(alpha)e-(E/RT) using reasonable hypotheses. The final formula is simple : E(T-b - T-10) - RT(b)(2) = 0. We can easily obtain the values of the thermal decomposition activation energy (E) and the onset temperature (T-i) from the non-isothermal DSC curves of any kind of energetic materials, and then calculate the critical temperature (T-i) of thermal explosion. The results obtained with this method coincide very well with the measured values for the common explosives HMX, RDX, Tetryl, and NTO as well as its ethylenediammonium salt (ENTO), potassium salt (KNTO), lead salt (PbNTO) and copper salt (CuNTO).