The disclosure discloses a skin-attached blood oxygen saturation detection system and a preparation method thereof. The system includes a front-end flexible blood oxygen saturation detection circuit and a back-end signal processing output module connected to each other. The front-end flexible blood oxygen saturation detection circuit uses a flexible packaging material to act as a packaging layer, a surface of the front-end flexible blood oxygen saturation detection circuit has an adhesive functional layer, and is configured to detect blood oxygen saturation of a human tissue through a reflective optical principle. The back-end signal processing output module is configured to transmit a blood oxygen saturation signal to a mobile terminal through a Bluetooth antenna transmission module.