To study the microstructure of nitrocellulose(NC) aerogel and its relationship with thermal properties, NC aerogel was prepared by sol-gel method and supercritical drying. The microstructure, crystallizability and thermal properties of the aerogel were characterized by SEM, XRD and TG/DSC-FTIR methods. Results show that: the microstructure of NC aerogel is nano-porous structure accumulated by nano-particles. The crystallization of NC is destroyed in NC aerogel, presenting amorphous disordered state. In comparison with NC, the DTG peak temperature and DSC exothermic peak temperature of NC aerogel shift 7 ℃ and 12 ℃ downwards, respectively, and the decomposition heat increases from 1429.87 J·g^-1 to 1689.21 J·g^-1.