Supposing the Frank-Kamenetskii parameter δ as stochastic variable of normal distribution, the thermal sensitivity probability density function of energetic materials was worked out, by the application of the probability density formula of monotone function, and the thermal safety degree of energetic materials was calculated. The results show that: the thermal sensitivity of energetic materials is not a normal distribution, but a kind of new probability density function decided by geometric factors (the characteristic measurement of reactant and geometric shape of reactant) and chemical factors (quantity of reaction heat, activation energy, density, frequency factor, and thermal conductivity), the value of safety degree is decided by the sensitivity distribution function.