Abstract: A series of nano antimony tin oxide (ATO)/polyvinyl butyral (PVB) composites were prepared using condensation reaction of polyvinyl alcohol (PVA) and butyraldehyde(BA) by in-situ method through dispersing the surface pretreated ATO in PVA solution with supersonic vibration. The structure, micro-morphology and properties of the nano-ATO/PVB composites were studied by using FTIR, UV/VIS/NIR (ultraviolet-visible-near infrared spectrophotometry), TG, TEM, AFM (atomic force microscope) and some other means. The results show that, a few nano-ATO particles added before the synthesizing of PVB resin can be uniformly dispersed in the matrix of PVB. The transmittance of the composites in ultraviolet light and near infrared light decreases obviously, but the visible light transmittance decreases slowly. The UV-shielding and heat-insulation performances increase continuously with the increase of nano-ATO content. For the lower ATO content (mass ratio 2.76% to PVB), the mechanical properties especially the toughness of the in-situ composites are markedly improved, the elongation at break increases by 7.3 times compared with PVB matrix. With the ATO mass ratio 1.74% to PVB, the visible light transmittance of the composite is higher than 70%, the ultraviolet transmittance is less than 10%, the transmittance of near infrared radiation is lower than 28%, the thermal conductivity is 0.23 W(m·K)^-1. The air temperature inside the box with the cover plate made of the ATO/PVB composites decreases by 5.5℃ compared with the PVB film without ATO, and the composite film also exhibits a good visible transmittance, excellent properties of UV-shielding and heat-insulation.