Abstract: Decomposition mechanisms of HONO elimination reactions of 1,3,3-trinitroazetidine(TNAZ) are investigated using density function theory(DFT).Two difference HONO elimination channels are acquired.The structure,frequencies,energies and zero-point-energy of reactant,transition-states and intermediates are calculated using B3LYP/6-31+G(d,p)level of theory.The calculated barrier heights of HONO elimination reaction are close to the active energy of TNAZ decomposition in solid state.Two HONO elimination channels may compete with each other.The HONO elimination reaction paths are predicted to be important for the decomposition of TNAZ in solid state.