To investigate the regulatory mechanism of amino and nitro substituents on the thermal stability of TYX series heat-resistant explosives， two novel heat-resistant explosives based on the bis（triazolo）tetrazine backbone-fully amino-substituted 2，7-diaminobis（［1，2，4］triazolo）［1，5-b：1'，5'-e］［1，2，4，5］tetrazine-5，10-diium-3，8-diide （TYX-1） and mono-nitro mono-amino substituted 2-amino-7-nitrobis（［1，2，4］triazolo）［1，5-b：1'，5'-e］［1，2，4，5］tetrazine-5，10-diium-3，8-diide （TYX-3）-were selected in this study. Their thermal decomposition behaviors were systematically compared using differential scanning calorimetry （DSC） and thermal decomposition kinetic methods， while the decomposition processes were comprehensively analyzed by thermogravimetry-infrared-mass spectrometry （TG-FTIR-MS）. The results show that the difference in substituents exerts a decisive influence on their thermal stability and decomposition pathways. TYX-1 exhibits a single high-temperature decomposition process with a peak temperature of 477.56 ℃ （at a heating rate of 20 ℃·min^-1）， and its decomposition mechanism conforms to the random two-dimensional nucleation growth model （A2）， consistent with the layered stacking structure promoted by amino groups and the resulting controlled two-dimensional energy release pathway. In contrast， TYX-3 shows a significantly lower decomposition temperature and multi-step decomposition characteristics： the initial stage follows a two-dimensional diffusion model （D2）， followed by a multi-reaction competitive stage， and finally transitions to a skeletal fracture process dominated by the one-dimensional chemical reaction model （F1）. Gas product analysis shows that the main decomposition products of TYX-1 are N₂， CO₂， N₂O， and HCN， while additional products including NO， HCNO， NH₂， and H₂O are detected for TYX-3， confirming that the nitro group， as a strong oxidizing moiety， induces an unconventional decomposition pathway and promotes the oxidative cleavage of the parent ring skeleton.