With the development of modern science and technology, higher requirements are put forward for radiation measurement of temperature, and multi-wavelength thermometry using wavelength closure to solve temperature has been widely used. However, it is difficult to determine the functional representation of the emissivity of the measured object to measure the real temperature. After introducing the concept of instrument measurement, the problem of determining object emissivity is transformed into a model of determining instrument emissivity. It is great progress in radiometric temperature measurement to construct the closed solution condition of real temperature using the wavelengths, which are the intersections of spectral distribution curves of emissivity of object and instrument. Based on this, a method of band integral is proposed to eliminate the influence of wavelength on temperature measurement caused by the binary function of object radiation, and the median wavelengths of the integral can replace the wavelengths of intersections. Combining with the “spectral color function”, the intersections of curves can be captured, and the measurement of real temperature is completed. It should be clear that the number of wavelengths required for temperature measurement is not the more, the better. By modifying the first and second radiation constants of Planck’s law, the generalized temperature measurement model is obtained, and the number of wavelengths required for measurement is limited to “3”, which can be used as the lower limit number of temperature measurement wavelengths required for the product of Planck’s law and emissivity series model. It is another breakthrough in radiation temperature measurement. The mathematical form on the definition level of object radiation represents the generalized model, and the connection between the generalized model and the emissivity of the linear instruments is realized. In the visible and near-infrared atmospheric window bands, the generalized model and instrument measurement equation is numerically fitted, and the adaptability of the definition and generalized model in the arbitrary band is verified. The experimental data of tungsten metal are simulated in the visible light bands. The results show that the generalized model can well restore the radiation data of tungsten by adjusting the limited undetermined parameters. The “spectral color function” design can realize the effective resolution of temperature measuring wavelengths. The relative temperature errors of tungsten are less than 0.15%, which proves that the temperature measurement method based on the intersection capture of the spectral distribution curve is an effective way to realize the real temperature radiometric measurement of objects.