In order to solve the problems of poor portability and inability to measure transient temperature of traditional multi-spectral radiation thermometers, a portable high-speed multi-spectral radiation thermometer was developed by adopting the spectroscopic method of splitting fiber+band-pass filter, and a high-speed photoelectric response circuit was designed. The results show that, the complexity of the system can be effectively reduced and the portability can be improved by using optical fiber and band-pass filter to replace the traditional prism and package it with other hardware of the thermometer. After assembly, the overall mass of the instrument is not more than 4 kg, and the volume is not more than 30 cm×25 cm×25 cm. The photoelectric conversion circuit with high bandwidth was designed, and the high-speed analog digital conversion chip, field-programmable gate array chip and CYUSB3014 chip were used for digital signal acquisition and transmission. The communication rate with the computer is up to 100 MHz, so that the thermometer can measure the temperature with microsecond change. The actual temperature measurement results of muffle furnace temperature after calibration show that the overall relative error of the thermometer is less than ±2.5% and the temperature measurement accuracy is high when the reference temperature is stable. This result is helpful to improve the portability of the thermometer and realize the high-precision temperature measurement of transient temperature field.