Abstract: The purpose of this paper is to study the microwave which passed in the plasma coaxial waveguide.Based on the analysis of boundary condition, the field function, character function, attenuation constant and some others meaningful are gained.The Matlab calculate soft was used to visualize the property of coaxial waveguide by plot.In definite condition, the relation of attenuation and the parameter of plasma, such as plasma frequency, collision frequency, incidence frequency of electromagnetic wave and dimension of waveguide were discussed comprehensively.