Abstract: This paper study the propagation characteristics of surface wave along a coated broad surface by using a RAM coated plane model.The complex propagation constants are formulated with eigenvalue function,which may be solved by iterative method.To explane in which manner the attenuation constant is depended upon the EM parameters of the material,a precise formula of attenuation is also derived and analyzed in detail.Finally,an efficient method for design wideband thin coated layer is presented which my be useful for practical purpose applications.