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.