Main characteristic parameter identification of polymer bonded explosive (PBX) failure is the basis for establishing strength criterion and evaluating structural strength. A series of uniaxial tension and compression-induced direct failure tests, and also failure after creep tests under different initial stresses, were designed within the temperature range of 20-50 ℃ on a type of TATB-based PBX. Based on the acquired failure data, effect of environment temperature and initial creep stress on the failure stress and strain was analyzed. Results demonstrate that for both direct failure and failure after creep: 1)With the increase of environment temperature, failure stress reduces both under tension and compression. Failure strain increases under tension but decreases under compression. 2) Given the same environment temperature, failure stress reduces and failure strain increases as the initial creep stress increases. This reveals that failure stress isn't an appropriate main characteristic failure parameter, because it fluctuates violently when environment temperature and initial creep stress change and has no critical value. On the contrary, failure strain is relative simpler as a main characteristic failure parameter. When strain reaches the critical strain, failure is generated no matter how loading history changes and what causes this strain (load or creep). Direct failure strain can be viewed as the critical failure strain at one temperature point. The critical failure strains at 20 ℃, 35 ℃ and 50 ℃ under uniaxial tension are 0.1330%, 0.1452% and 0.1675% respectively, and it changes to -1.4206%, -1.4159% and -1.1731% respectively under uniaxial compression.