At present, most of the non-invasive monitoring equipment for cerebral blood oxygen in clinical use is dual-wavelength. Because the absorption of melanin will cause deviations in the measurement results, the measurement results need to be corrected. For this reason, based on the basic principle of non-invasive monitoring of cerebral blood oxygen by near infrared spectroscopy, in view of the shortcomings of existing non-invasive monitoring equipment for cerebral blood oxygen, considering the optical characteristics of the prefrontal lobe, a four-wavelength detection light source (700, 760, 805, 850 nm) and a dual-channel photoelectric detector for noninvasive monitoring of cerebral blood oxygen, and a mathematical model of spectral absorbance is established. On this basis, a new type of non-invasive monitoring system for cerebral blood oxygen is constructed, which can inhibit the interference of skin melanin components to non-invasively measure the cerebral blood oxygen information. Finally, through the rank sum analysis of the Valsalva exercise and noload control experiments, the effectiveness of the system is preliminarily verified.