A sol-gel method was employed to improve wood surface properties by generating SiO2 with tetraethoxysilane and methyl triethoxysilane as co-precursors. The effect of SiO2 on the wood surface properties was studied by the analysis of size stability, ultraviolet radiation aging resistance, and contact angle of the modified wood. The improvement mechanism was explored using scanning electron microscopy (SEM), energy dispersive X-ray (EDAX), and Fourier transform infrared spectroscopy (FT-IR). The results showed that the water absorption and the hygroscopic expansion rate of the modified wood were less than those of the control samples. The discoloration resistant properties were improved 1.5 times more than that of the control samples. The thickness of SiO2 on the wood surface was approximately 60 μm, and the silicon content increased as the dipping time increased. The contact angle of modified wood showed that it was more hydrophobic than that of the control sample, and this increased as the dipping time increased. The variation in contact angle of the modified wood was less than that of the control sample before and after aging. The anti-aging performance of the modified wood surface was also improved.