A method for preparing an optical recording medium of phase change type is provided. This recording medium comprises a substrate, a recording layer, and a lower and an upper dielectric layers provided in direct contact with the recording layer. In this method, a step of an exposure treatment wherein the surface of the lower dielectric layer is exposed to an oxidative atmosphere is conducted after forming the lower dielectric layer on the substrate and before forming the recording layer on the lower dielectric layer. A step of a heat treatment wherein said lower dielectric layer is heat treated may be carried out in addition to the exposure treatment.