We simply synthesized the triethoxysilane bearing the second-order nonlinear optical(NLO) active chromophore in the side chain. In order to improve the poor temporal stability of second-order NLO effect, we introduced the thermal crosslink between the side chain themselves. We prepared two different silane solutions; one is composed of triethoxysilane with NLO chromophore (SGDR1) only. The other consists of SGDR1 and 3-glycidoxypropyl trimethoxysilane. Thermal crosslink formation was traced with in-situ infrared spectroscopy. We achieved much improvement of the temporal stability of second-order NLO effect utilizing this crosslinked composite system.