In the separation process of temperature and emissivity from spectra data, there is an underdetermined problem, N equation containing N+1 unknown number. In this paper, Newton’s method is used to inversion calculate the surface temperature and the emissivity of the material. The iterative formula is established with Taylor series linear terms. Given the initial temperature and emissivity, an approximate solution of temperature and emissivity is obtained through iteration. In this paper, the Theoretical value of thermal radiation and the experimental data of cavity blackbody were used to verify ,the results show that the inversion temperature obtained with the given any initial values of temperature and emissivity are close to the true temperature. The relative error is lower than 0.09. For different emissivity models, the lineshape of the inversion emissivity is consistent with that of the true emissivity. The initial values of temperature and emissivity are closer to the true temperature and emissivity, which gives rise to more accurate inversion results. This method eliminates the emissivity assumed model limits. It is expected to be used the inversions of the surface temperature and the emissivity of the material based on the thermic spectra in high temperature and ultra high temperature.