In order to break the energy limitation of nitrocellulose(NC) and improve its low-temperature mechanical properties by decreasing the glass transition temperature, NC with azide side chains called PA-IPDI branching NC was synthesised. via isophorone diisocyanate (IPDI) first reacted with residual hydroxyl on NC, and then reacted with the introduced 2,2-bis azido methyl 1,3-propanediol (PA). Its molecular structure, energy performance, thermal stability and dynamic mechanical properties of PA-IPDI branching NC were studied by IR, elemental analysis, TG, DSC and DMA, respectively. The results show that the released heat per mass unit of modified NC of 1466 J·g^-1 is nearly two times more than unmodified NC with 11.75%N. The calculated value of heat of detonation of modified NC ( 4434 kJ·kg^-1) is higher than that of 1^# NC (4152 kJ·kg^-1). The glass transition temperature of modified NC (117.3 ℃) is lower than that of unmodified NC with 11.75%N(140.2 ℃), the tensile modulus of modified NC is higher than that of unmodified NC within ± 60 ℃. It is suggested that PA-IPDI modified NC is an excellent substitute of NC.