Emissivity is very important in the data processing of a multispectral thermometer, but it is very difficult to be obtained because of the influence of various factors. In this paper, an emissivity model based on wavelet network is established by combining the wavelet network with the multispectral theory. The simulation result of the method is in good agreement with the hypothesis. The test result has shown that this method is a good method for obtaining the emissivity of objects.