The thermal decomposition processes of PETN and GI-920 explosives were studied by DSC-TG at heating rates of 5,10 and 20 K·min-1,respectively. The thermal decomposition kinetic parameters and the mechanism function of PETN and GI-920 explosives were obtained by Ozawa′s method and the integral isoconversional non-linear method. The results show that the thermal decomposition mechanism of PETN and GI-920 explosives is classified as random nucleation and growth. The initial temperatures of the thermal decomposition of GI-920 explosive are approximately the same on TG curves with the different heating rates. DSC curve of the GI-920 explosive reveals an endothermic melting peak and an exothermic decomposition peak. The GI-920 explosive have good thermal stability below 130 ℃. The activation energy,pre-exponential factor and mechanism function of the thermal decomposition process of GI-920 explosive are 156.02 kJ·mol-1，1.934×1017 s-1 and f(α)=4/3(1-α)［-ln(1-α)］1.-4,respectively. The thermal decomposition kinetic equation is dα/dt=2.579×1017×(1-α)［-ln(1-α)］1.-4exp(-1.876×104.-T).