To improve the thermal shock resistance of TATB-based polymer bonded explosive (PBX), TATB-based PBX was modified by styrene copolymer. The tensile mechanical properties and thermophysical properties of TATB-based PBX and its formulation modified by styrene copolymer were analyzed, and the thermal shock resistances of formulation before and after modification were compared. The thermal conductivity behaviors of TATB-based PBX and its styrene copolymer modified formulation were simulated by Agari series model. Results show that the addition of styrene copolymer with high glass transition temperature and high mechanical strength can improve the tensile strength and elastic modulus of TATB-based PBX and simultaneously reduce the linear expansion coefficient and thermal conductivity of TATB-based PBX. The results predicted by theoretical model are in good agreement with the experimental data. After the addition of styrene copolymer of mass fraction as 1%, the thermal stress resistance factor of TATB-based PBX at normal temperature increases from 10.72 W·m^-1 to 13.16 W·m^-1. With the increase of temperature, the thermal shock resistances of TATB-based PBXs decrease gradually. The thermal stress resistance factor of TATB-based PBX decreases significantly in the temperature range of glass transition from 323 K to 343 K. The addition of styrene copolymer can restrict decreasing extent of the thermal stress resistance factor of TATB-based PBX in the temperature range of 323 K to 343 K.