A quantitative non-destructive tissue oxygen detection system based on Near Infrared Spectroscopy (NIRS) was proposed. By using a micro-spectrometer to replace the traditional signal receiving and processing part, the wavelength of the light source was measured in real time. The influence of the environment was compensated by a compensation algorithm. After the calculation of output spectral signals processed by mean and FFT filtering, the tissue oxygen concentration was obtained. In the forearm occlusion experiment, the effectiveness of the measurement results of Regional Saturation of Oxygen (rSO2) was verified. The measurement results were consistent with the theory. This showed that the NIRS technology based on the spectrometer could monitor rSO2 better and its adaptability was better than that of traditional methods.