Nano silica (SiO2) sol was synthesized through a sol-gel process. Then nano silica sol was modified by KH-570. Polyurethane-acrylate/SiO2 composite latex (SPUA) with core-shell structure was synthesized with modified nano silica, acrylate and polyurethane prepolymer end-capped by double bond by in situ polymerization. The structure of the copolymer was characterized by Fourier transform infrared spectrometer (FTIR). The particle morphology of the SPUA latex was observed through transmission electron microscopy (TEM). Contact angle measuring instrument, tensile testing machine，scanning electron microscopy (SEM) and thermo gravimetric analyzer were performed on the film to test the contact angle to water, mechanical properties, surface appearance and thermal properties of the SPUA films. The results indicated that, with increasing the mass fraction of modified nano silica, the mechanical properties and the thermal stability of the films were improved obviously. When the mass fraction of modified nano silica was 8% in the film,the temperature for the maximal thermal mass-loss rate was 413℃,water absorption was 4.1%, contact angle was 71.5°,the tensile strength of the SPUA film was 17.7MPa and the hardness was 93%.