Real-time updates of metrical data can not generally be realized in the commonly used methods for calculating the pulse wave of blood oxygen saturation. Based on the hardware platform of pulse wave signal from NJL5501R, and high linear correlation of the red laser and infrared light collected in pulse wave signal measurement, an approach to determine the value of the blood oxygen saturation is proposed in the present paper by establishing the linear regression model of the red laser and infrared light. The effect of the sampling number of pulse wave signal in calculation on the characteristic parameters of pulse wave is also analyzed. The experimental results showed that the approach could guarantee the measuring accuracy and realize the fast updates of blood oxygen saturation data. This paper provides an effective method for real-time and accurate monitoring of pulse blood oxygen saturation in human body.