The process of the radiation temperature measurement data is to understand the relationship between the spectral emissivity and the true temperature. If the spectral emissivity model is not in conformity with the actual spectral emissivity model, the large temperature measurement error will be occured. Therefore, it is one of the main problems to be solved in this field in terms of how to reduce the dependence of the spectral emissivity and the true temperature on the measurement model. The paper puts forward an algorithm, which can find out the spectral emissivity and the true temperature without the assumption of the model relationship between the emissivity and wavelength. Through simulation and experiment, the results show that this algorithm can be used to solve a relatively reasonable spectral emissivity and meet the requirements of a certain precision of true temperature.The algorithm has the features of being simple, reliable, universal, and suitable for spectral measurement of emissivity and the true temperature.