Colorimetric thermometry is a useful method for high temperature measurement. In this paper, a high precision multicolorimetric pyrometer is introduced. A multicolorimetric calculation without the gray body assumption is deduced. A novel photoelectric MOSFET with direct ac signal output is employed as the sensor, which works near the visible waveband and brings smaller uncertainty under the Wien approximation than the infrared radiation detectors. A dual-processor embedded signal process circuit is constructed, which ensures the pyrometer's portability as well as supports the accuracy of colorimetric calculation. Through the tests, the precision of the pyrometer is better than $3{^{0}\!\!/\!{\scriptstyle00}}$ in the temperature range 1323–1923 K.