Abstract: The study of the radiation characteristics of an object requires several physical property parameters of the object, including its emissivity. Test data are usually limited by test circumstances and can not meet the requirements for emissivity numeric simulation. This article creates an academic computational method. First, it explores the theory of electromagnetic waves transmitting in metals combined with a free-electron model of metals. Then it discusses the dispersive relation of optical constants and the complex refractivity in the light incidencing from air to metal, and performs a random simulation of a rough metal surface. Furthermore, it discusses the various factors which affect the regular law of metal spectral emissivity. Compared with similar tests and numeric data, this method for computation of any kind of metal emissivity is credible and widely applicable.

Key words: metal material, emissivity, optic parameter, rough surface, numeric simulation