In this paper, in order to rapidly measure the temperature of a high-temperature target in real time without emissivity data, a high-precision multispectral radiation temperature measurement method based on the improved grey wolf optimization (IGWO) algorithm is proposed. The method can automatically identify the emissivity models of different trends and realize the simultaneous estimation of temperature and emissivity without the emissivity hypothesis model. The IGWO algorithm is applied to the temperature test of a silicon carbide and tungsten material. The temperature test results show that the absolute and relative errors of the silicon carbide (the tungsten) are less than 3 K (4.5 K) and 0.25% (0.18%), respectively. The average time of the algorithm is 0.28 s. The IGWO algorithm can be expected to be applied to some high-precision temperature measurement scenarios.