The pulse oximeter used to measure patients oxygen saturation non-invasively and continuously, has numerous applications in clinic care. The pulse oximetry measurement combines two basic methods, spectrophotometry and photoplethysmography (PPG). The red light and the infrared light are exposed to the ear lobe, finger or other tissue with fluctuation of artery blood, and then detected. The amplitude ratio of the photoplethysmography waveform of red light and infrared light varies with the oxygen saturation of blood. The measuring principle of the pulse oximeter is based on traditional test method, its accuracy is not gratifying due to various factors influencing the measurement result, such as the principle, measuring condition, and individual discrepancy. In the present paper a new pulse oximetry based on dynamic spectroscopy is introduced, It can promote the accuracy of the pulse oximeter evidently. The dynamic spectroscopy method is able to eliminate the interference of individual discrepancy and measuring condition in principle. This new method can eliminate the measurement error of pulse oximetry theoretically.