We have investigated the oxidation behavior of epi-Si0.7Ge0.3 films in dry oxygen ambient. Epi- Si0.7Ge0.3 films about 500Å in thickness were deposited on (100) Si wafers by UHV-CVD system. Oxidation was carried out in a conventional tube furnace at 800 °C . In this study, it was found that Ge piles up at the oxide/substrate interface, forming a Ge-rich layer. Because of the large difference in the heat of formation between SiO2(-730.4KJ/mol at 1000K) and GeO2(-387.07 at 1000K) , the Si is to be more reactive than Ge to oxygen. The oxidation rate of SiGe in a dry oxygen environment is found to be essentially the same as that of pure Si.