An accurate thermal expansion coefficient (α) of a thin film is important in the design of microelectronic devices and microsystems. In this research, we present the use of microbridge buckling deformation caused by residual stresses to determine the α of a thermal oxide (SiO2) film. The determination of α is supported through experimental means and the analysis by finite-element method (FEM) of the buckling profiles of a microbridge. Moreover, to obtain the α of a thermal SiO2 film accurately, a nanoindentation system and an optical microscope with a high-resolution gauge were used to determine the elastic modulus of the thermal SiO2 film and the α of the silicon substrate, respectively. By combining micro-electro-mechanical systems (MEMS) technologies and FEM with thermomechanical analysis, the α of the thermal SiO2 film was calculated. The measured α of the thermal SiO2 film at room temperature is 0.24×10–6/℃ with a standard deviation of 0.02×10–6/℃.