In order to improve the oxidation resistance of 304 stainless steel, SiO₂ thin films were prepared on the stainless steel surface by sol–gel method using tetraethyl orthosilicate (TEOS) as raw material. The effect of coating number on the high-temperature oxidation resistance of stainless steel at 900℃ was studied. X-ray diffractometer (XRD), oxidation kinetics, and scanning electron microscope (SEM) analysis results show that the SiO₂ film effectively reduces the oxygen partial pressure at the interface between the substrate and the film, and promotes the selective oxidation of the stainless steel surface to produce Cr₂O₃ and NiCr₂O₄ with good high temperature resistance. Furthermore, the high temperature oxidation resistance of stainless steel is significantly improved. The sample coated with three layers of SiO₂ film has the best high temperature oxidation resistance. Too many coating layers increase the internal stress of the film, which will cause cracks and peeling of the film to reduce the high temperature oxidation resistance of stainless steel.