Isowurtzitane derivatives are currently one of the most potential cage energetic compounds.In order to systematically study the high temperature thermal decomposition law of isowoodsane derivatives and clarify their detonation mechanism， in this work， the thermal decomposition properties of hexanitrohexaazaisowurtzitane （ε-CL-20）， 4，10-dinitro-2，6，8，12-tetraoxa-4，10-diaztetracyclododecane （TEX） and 4，10-diazomethyl-2，6，8，12-tetranitrohexaazaisowurzane （BATNIW） under high temperature（1500-3500 K） were studied by molecular dynamic simulations with ReaxFF-lg reactive force field and molecular dynamics method. The results show that the denitro and ring opening are the main initial reactions of ε-CL-20， TEX and BATNIW， in which the ring opening mainly occurs at the C─N bonds or C─O bonds of the five membered rings. Among the decomposition products， the yields of CO₂ and H₂ change significantly under different temperature， while content of N₂ are similar at temperature higher than 3000 K. The decomposition of BATNIW produced N₂ with the highest reaction rate and the maximum yield. During the thermal decomposition of TEX， clusters could easily be produced， and glyoxal could be regarded as its characteristic product. The order of thermal decomposition activation energy of the three derivatives is TEX > BATNIW > ε-CL-20， which suggests TEX shows the best stability. This work preliminarily reveals the relationship between the molecular structure and thermal decomposition of three isowurtzitane derivatives.