A fractal model of thermal conductivity for polymer bonded explosive(PBX)particles was established based on the fractal theory and random distribution filling model, and the thermal conductivity of TATB based PBX with different mass fraction such as 20%, 40%, 95%, ect, was calculated and compared with those measured by the flash method, and those from semi Hamilton-Crosser model with shape factor of 3.Results show that the errors between the calculated and the measured were 20.2%, 32.8%, 15.0% with the mass fraction of 20%, 40% and 95%, respectively.The thermal conductivity of PBX increases with the increase of mass fraction of TATB.The calculation results based on fractal model is better than that obtained by the semi-Hamilton-Crosser model.