The invention discloses a high-precision dissolved 
oxygen sensor based on a fluorescent method. The high-precision dissolved 
oxygen sensor comprises a data processor, a reference 
light source, an excitation 
light source, a communication circuit and a probe, wherein the communication circuit is communicated with third equipment, the probe is in 
bidirectional communication connection with the data processor, and a 
signal output end of the data processor is respectively connected to the reference 
light source and the excitation light source through a path selective circuit; the reference light source and the excitation light source are connected with a 
signal input end of the data processor through a 
light guide rod, a fluorescent film, a 
photoelectric conversion circuit, a filter circuit, an amplifying circuit and an analog-to-
digital conversion circuit sequentially; the data processor is used for reading conversion results of the analog-to-
digital conversion circuit in real time and respectively calculating out a phase phi1 and a reference phase phi2 according to the conversion results; a 
phase difference phi can be obtained through the phase phi1 and the reference phase phi2; finally, a dissolved 
oxygen concentration Cdo can be solved. The dissolved 
oxygen sensor disclosed by the invention achieves long-time unattended remote monitoring. The 
phase difference is utilized to calculate out the dissolved oxygen concentration, so that the measurement accuracy is improved.