The work aims to improve the dimensional stability of plywood and enhance the hydrophobicity of plywood, so as to broaden its application field and scope. The sodium silicate solution was mixed with vinyl triethoxy silane to form a mixture of different ratios of substances. The organosilicon polymer was obtained by stirring, condensing and restirring and then the plywood was impregnated. The content of hydroxyl group on the surface of plywood before and after modification and its modification mechanism were analyzed by Fourier transform infrared spectrometer. The surface morphology of modified plywood was characterized by environmental scanning electron microscopy. Universal mechanical testing machine was used to explore the mechanical properties of plywood before and after modification. The wetting characteristics of the plywood before and after modification were compared with the contact angle tester, and the water absorption rate and thickness expansion rate were calculated. Organosiloxane was successfully bonded to the surface of plywood. The mechanical properties of the plywood had no significant change before and after modification. The water absorption rate and thickness expansion rate of the plywood treated under the ratio of substances of 2∶5 were lower. In the contact angle test, the initial contact angle of the plywood treated under the ratio of substances of 2∶5 reached 156.8° and was still 140.3° after 60 s, maintaining the superhydrophobic state. The hydrophobic properties and dimensional stability of the plywood treated with organosilicon polymer are improved greatly.