In this paper, a multi-channel spectral detection system is designed to address the need for multi-spectral radiometric temperature measurement of high temperature targets over long distances. The front end of the system uses a bi-reflective Cassegrain structure to collect the spectral radiation of the target, while the back end includes a long-wave infrared imaging targeting system for target location and a dual-band spectral system operating at 380~1050 nm and 980~2550 nm respectively. The spectral system adopts Czerny-Turner structure, with a resolution better than 5 nm in the 380~1050 nm band and 15 nm in the 980~2550 nm band, and the number of spectral channels is greater than 220. The 400 m target outfield experiments and the 700~2300 ℃ high temperature blackbody temperature experiments show that the multi-channel spectral detection system is capable of targeting and spectral detection of long-range targets. The multi-channel spectral detection system designed in this paper is expected to be used for long-range temperature detection on the ground, in aviation and in space.