The invention discloses a reflection-based blood oxygen measurement method. The measurement method comprises the steps of step 1, emitting a nano-beam through a transmitting end of a reflective SPO2 sensor to enter a human body tissue; step 2, removing interference of the noise on the nano-beam reflected in step 1 through a median filter; step 3, using the receiving end of the reflective SPO2 sensor in step 1 to receive the reflected nano-beam; step 4, converting a current signal received by the reflective SPO2 sensor into a voltage signal; step 5, using a built-in A/D of a single chip to convert the voltage signal in step 4 into a digital signal; step 6, performing an independent element analysis method (ICA) for data preprocessing, analysis and calculation on the digital signal in step 5by using the single chip; step 7, separating a valid signal associated with SpO2 calculation from mixed data. The method has the advantages of being fast in detection speed, strong in practicability,convenient to produce and suitable for wide application and popularization.