The invention provides a cathodic protection automatic monitoring system of a petroleum storage tank, belongs to the technical field of petroleum chemical engineering, and solves the problem of shortage of effective methods for accurately detecting a cathodic protection system of the petroleum storage tank in real time in the prior art. The cathodic protection automatic monitoring system of the petroleum storage tank comprises multiple auxiliary anodes, multiple reference electrodes, a voltmeter, a potentiostat, a control module and an upper computer; all the auxiliary anodes are electrically connected with a positive pole of the potentiostat; a tank body is electrically connected with a negative pole of the potentistat; each reference electrode is connected with the tank body through the voltmeter; the voltmeter is connected with the control module; and the control module is connected with the upper computer. The cathodic protection automatic monitoring system of the petroleum storage tank has such advantages as detection timeliness, accuracy and reliability.