The invention discloses a fluorescence-method dissolved oxygen sensor, which comprises a measuring light path, a signal processing circuit, a shell body, an outgoing cable and a temperature sensor, wherein the measurement light path comprises a fluorescent film, an optical filter, a photoelectric detector, an excitation light source and a reference light source; the fluorescent film comprises a waterproof breathable film, a fluorescent layer and a colorless transparent glass sheet, the inner surface of the waterproof breathable film is coated with the fluorescent layer, and the colorless transparent glass sheet is bonded to the inner surface of the fluorescent layer; the fluorescent film is located at the head part of the shell body, the optical filter is located between the fluorescent film and the photoelectric detector, and the photoelectric detector is located behind the optical filter and connected with the signal processing circuit; the reference light source and the excitation light source are fixed on two sides in the shell body and are positioned on the same horizontal plane with the optical filter; and the temperature sensor is arranged on the inner wall of the shell bodyand is fixed between the optical filter and the fluorescent film. According to the fluorescence-method dissolved oxygen sensor, the fluorescent film can be prevented from falling off, much diffused light and secondary reflection are avoided, and the measurement precision and stability are improved.