The surface plasma waves (SPW) resonance is a sensitive function of the optical constants of metallic films and their surface conditions. Thus, the optical constants of metallic films and contamination layers on its surface could be determined precisely by using the SPW technique. In this paper, analysis and theoretical calculation of the SPW with traditional thin film optics are discussed. The Kretschmann arrangement is used to measure the SPW resonance reflectance. And with aid of an optimization method the optioal constants are calculated. Some experimental results on Ag，Au, Cu, Al and surface layers, such as AgaS, CuO2 and Al2O3 are given.