The invention relates to the field of dissolved 
oxygen content detection, in particular to a three-
electrode electrochemistry dissolved 
oxygen sensor. The sensor comprises a cylindrical shell of the sensor, a replaceable 
oxygen permeation membrane, a membrane cover, a gold 
electrode, a sliver 
electrode and a 
platinum electrode, wherein the gold electrode is arranged in the cavity of the cylindrical shell to serve as a 
working electrode, the sliver electrode serves as an 
auxiliary electrode, the 
platinum electrode serve as a sliver protection electrode, and the 
silver electrode, the gold electrode and the 
platinum electrode are independently connected with a polarization circuit through leads; the cavity of the cylindrical shell is full of a liquid reaction 
electrolyte, wherein the 
electrolyte reaction liquid comprises the following ingredients in parts by weight: 74.55 parts by weight of 
potassium chloride, 0.561 parts by weight of 
potassium hydroxide and 1000 parts by weight of water.By use of the 
electrochemistry dissolved 
oxygen sensor disclosed by the invention, in a measurement process, oxygen in a 
water sample is not consumed, detection accuracy is improved, an 
auxiliary electrode adopts a double-
helix structure to increase a contact area with the 
electrolyte, the response speed of the sensor is improved, the sensor adopts a three-electrode 
system structure, the electrolyte in the electrolyte is not consumed, the silver of the 
auxiliary electrode is not consumed, and the service life is greatly prolonged.