The dissolved oxygen water quality sensor is based on the principle of fluorescence quenching. When light shines on the fluorescent material, the fluorescent material will be excited and emit red light. Since oxygen molecules can take away energy, the time of excited red light is inversely proportional to the concentration of oxygen molecules. The concentration of dissolved oxygen can be calculated by measuring the duration of red light. WQS-DO sensor can meet all the requirements of field operation and long-term or short-term test. On the premise of not consuming oxygen, fluorescence technology can provide users with accurate measurement data for all measurement environments, especially those with low oxygen concentration.