The apparent spectral emission of a semi transparent medium layer with a sine shaped surface was analyzed by the pseudo source adding method. The isotropic and isothermal medium layer was investigated by considering a specular and semi transparent sine shaped surface as well as a diffuse and opaque substrate wall. The pseudosource adding method was improved. The apparent hemispherical and directional spectral emissivity results were presented and discussed by considering the influences of relevant factors. The pseudo source adding method was found to be very effective for the analysis of the thermal emission of the semi transparent medium layer with curved surface.