In this study, the nano barium sulfate (Nano-BaSO 4 ) as an inorganic filler, polybutylene terephthalate (PBT)/polyethylene terephthalate (PET)/Nano-BaSO 4 composites were prepared by melt blending. The effect of Nano-BaSO 4 on the properties of PBT/PET blends was studied by thermal deflection temperature tester, differential scanning calorimeter, thermogravimetric analyzer, rotational rheometer, electronic universal tensile testing machine, pendulum impact testing machine and other instruments. The results showed that when PBT:PET was set as 90:10 wt% and Nano-BaSO 4 content was 4 wt%, the heat deflection temperature of the composites was the highest, which was 22.6% higher than that of the PBT/PET blends, and the heat resistance was the best. When the content of Nano-BaSO 4 was 2 wt%, the comprehensive mechanical properties of the material were the best.