By using the technique of wavelet transform for pretreatment and flitting the weak radiation signal has been accurately detected. Moreover, a new method for modeling the emissivity and wavelength of a multiwavelength pyrometer has been proposed and developed for obtaining accurately spectral emissivity and wavelength. In this method, it was unnecessary to give sample data of fixed emissivity model. Then, the detailed aglorithem was described and the simulation was done for checking the validity of algorithm.