Abstract: A fast method of blood oxygen saturation detection for wearable smart mobile devices was proposed.Based on the no-correlated relationship between the pulse component of photoplethysmography and the noise component,the noise can be suppressed and the blood oxygen saturation can be calculated.The method has been verified by processing the low perfusion signal from the blood oxygen simulator.The results show that this method has a small amount of calculation with good anti-noise ability.It can accurately detect the blood oxygen saturation from weak signals with noise.