This study conducted in-situ micro-CT characterization experiments on HTPB propellant under wide temperature range and uniaxial tension conditions. The mesoscopic dewetting damage behavior of the propellant with three environmental temperatures of -20 ℃， 20 ℃， and 50 ℃ was analyzed， and a three-dimensional mesoscopic representative volume element model based on the volume proportions of the mesoscopic components of HTPB propellant was constructed. The stress-strain relationship and dewetting proportion-strain relationship of the model for different temperatures and strain rates were analyzed. It was found that HTPB propellant had more severe dewetting at low temperatures （-20 ℃）， with the filler/matrix interface dewetting proportion of nearly 30% when the propellant specimen fractured， while the porosity was only 6%. Through numerical simulation， it was found that the propellant undergoes more severe dewetting with low temperature and high strain rate， which greatly deteriorates the mechanical properties of the propellant. By comparing experimental and simulation results， the numerical model constructed in this paper can effectively predict the dewetting damage behavior and macroscopic mechanical properties of propellants.