Oxidation behavior of alloy 316L stainless steel static capsules were investigated by long-term exposure to the supercritical water at 500 degrees C and 25 MPa for various exposure times. It was found that the thickness and weight gain vs. exposure time followed parabolic law. Elemental and phase analyses indicated that long-term exposure to the SCW resulted in formation of scales identified as Fe3O4 (outer layer), Mn-Fe-Ni-Cr spinel (inner layer) on the substrate, and Ni-enrichment (chrome depleted region) in the alloy 316L. Oxidation phenomena and scales grown on the Alloy 316L as the result of long term exposure to the supercritical water was discussed.