Hexanitrohexaazaitsowurtzitane(HNHAIW) was heated at 100℃ for 48, 96and 300h, respectively. No burning or explosion occurred during heating. The crystals had no visible appearance change and no crystal configuration transition identified by means of FTIR analysis. The weight loss of 0. 02% after 96h heating indicates that the thermal stability of ε-HNHAIW is better than that of RDX and HMX.