With the help of the onset temperature (T_e) and maximum peak temperature (T_p) from the non-isothermal DSC curves of tri-base gun propellants M32 and SD at different heating rates (β),the thermal decomposition activation energy (E_K and E_O) and pre-exponential constant (A_K) obtained by Kissinger′s method and Ozawa′s method,the values of specific heat capacity (C_p),density (ρ) and thermal conductivity (λ) obtained by the specifications of standardization method GJB 772A-97-406.1, 401.2 and 409.1, the decomposition heat (Q_d,taking half-explosion heat),Zhang-Hu-Xie-Li′s formula, Smith′s equation andWang-Du′s formulas,the values(T_e0 and T_p0) of T_e and T_p corresponding to β→0,thermal ignition temperature (T_TIT),adiabatic time-to-explosion (t_TIad),thermal sensitivity probability density function ［S(T)］ versus temperature (T) relation curves for infinite cylindrical and spheroidic tri-base gun propellants M32 and SD with radius of 0.05m surrounded with surrounding of 373 K,peak temperature corresponding to the maximum value of S(T) versus T relation curve (T_S(T)max),safety degree (S_d) and critical thermal explosion ambient temperature (T_acr) of tri-base gun propellants M32 and SD are obtained. The results show that the thermal safety of tri-base gun propellant SD is greater than that of tri-base gun propellant M32,and the accelerating tendency from adiabatic decomposition to explosion of the latter is poorer than that of the former.