Abstract: CO is one of the main products of hydrocarbon combustion. Accurate measurement of CO concentration at the scramjet outlet is an important basis for evaluating the combustion efficiency of the hydrocarbon fuel. Compared with the near infrared band, the CO absorption spectrum in the mid infrared band has the advantages of stronger absorption, rich spectral lines, relatively isolated spectral lines and no interference from other gases. Based on the mid infrared absorption spectrum technology, this paper studies the mid infrared spectrum characteristics of CO, selects the characteristic spectrum which is suitable for the measurement of CO in the high temperature flow field, designs and builds the CO concentration detection system in the high temperature flow field, carries out the CO measurement verification under different equivalence ratios of the plane flame, realizes the CO measurement of the high temperature flow field at the exit of a scramjet, and reflects the changes of concentration and temperature of CO during the combustion of aviation kerosene, thus providing powerful research means and abundant experimental data for the study of combustion and flow mechanism of the scramjet.