Abstract: In order to improve the heat insulation performance of polycarbonate (PC) and maintain the high transparency at the same time, a series of silane coupling agent KH-570 modified nano antimony doped tin oxide (ATO)/PC composites were prepared by sol-gel method with infrared blocking agent of nano ATO. The particle size distribution and dispersion of nano ATO in PC matrix were investigated by laser particle size distribution analyzer and SEM. Meanwhile, tensile testing machine, spectrophotometer and insulation effect simulator were used to determine the mechanical properties, transmission properties and heat insulation performances of composites. The results show that silane modified nano ATO disperses in PC matrix uniformly. The tensile strength and impact strength maintain at 60.0 MPa and 16.0 kJ·m^-2 or more, respectively. With the mass fraction of nano ATO increasing, the performances of infrared blocking and heat insulation enhance. When the content of nano ATO is 0.5wt%, the visible light transmittance of nano ATO/PC composites is over 80%, and the temperature difference between inside and outside of insulation effect simulator is up to 3.9 ℃.