Based on infrared spectral absorption technique, a carbon monoxide (CO) detection system was developed using the fundamental absorption band at the wavelength of 4.6 μm of CO molecule and adopting pulse-modulated wideband incandescence and dual-channel detector. The detection system consists of pulse-modulated wideband incandescence, open ellipsoid light-collector gas-cell, dual-channel detector, main-control and signal-processing module. By optimizing open ellipsoid light-collector gas-cell, the optical path of the gas absorption reaches 40 cm, and the amplitude of the electrical signal from the detector is 2 to 3 times larger than the original signal. Therefore, by using the ellipsoidal condenser, the signal-to-noise ratio of the system will be to some extent increased to improve performance of the system. With the prepared standard CO gas sample, sensing characteristics on CO gas were investigated. Experimental results reveal that, the limit of detection (LOD) is about 10 ppm; the relative error at the LOD point is less than 14%, and that is less than 7.8% within the low concentration range of 20~180 ppm; the maximum absolute error of 50 min long-term measurement concentration on the 0 ppm gas sample is about 3 ppm, and the standard deviation is as small as 0.18 ppm. Compared with the CO detection systems utilizing quantum cascaded lasers (QCLs) and distributed feedback lasers (DFBLs), the proposed sensor shows potential applications in CO detection under the circumstances of coal-mine and environmental protection, by virtue of high performance-cost ratio, simple optical-path structure, etc.