The lower limit of the existing multi-spectral pyrometer is higher than 1 173 K (900 ℃), which is not suitable for the measurement of the true temperature range of a new rocket plume (900~2 700 K). A wide-range multi-spectral pyrometer for true temperature measurement of the solid rocket engine plume is developed to solve the problem that existing multi-spectral pyrometers cannot measure the plume true temperature when the temperature is lower than 1 173 K. The pyrometer uses a parallel connection method of the photoelectric detectors adjacent pixels, and proposes a temperature calibration method for 900~1 173 K region on the basis of the logarithmic function, so as to broaden the range of the measuring temperature pyrometer. The field measurement is carried out on the three targets of a solid rocket engine plume and the experimental results verify the validity of the pyrometer.