Trimerizing furoxans are ideal molecular skeletons for the construction of high energetic substances due to their compact structures and high enthalpy of formations. Herein, we reported the first systematic research on the thermochemical behaviors and decomposition mechanism of energetic trimerizing furoxan structures of 3,4-bis(3-fluorodinitromethylfuroxan-4-yl)furoxan (BFTF), 3,4-bis(3-cyanofurazan)furazan oxide (BCTFO) and benzotrifuroxan (BTF). Both the substituted furoxan based energetic compounds (BCTFO and BFTF) exhibited low melting points and complicated thermal decomposition behaviors, while the melting point of unsubstituted furoxan (BTF) was much higher. Their detailed mechanism were proposed based on the experimental results through in-situ FTIR spectroscopy method and DSC-TG-FTIR-MS quadruple technology, which indicated that the cleavage of substituent would trigger the decompostions of BFTF and the decompostion of trimerizing furoxan skeletons almost synchronous occurrence with substituents in BCTFO. The self-oxidation-reduction of the linear and annular trimerizing furoxans lead to similar decomposition fragmented small molecule products.