The present invention discloses a distillation apparatus tower top system dew point corrosion test method. The method is as follows: 1) processing a working electrode and a corrosion coupon; 2) an etching solution is poured into a five-necked flask, a second (II) three-electrode system is fixed in three mouths of the five-necked flask, the five-necked flask is fixed in a numeric display oil bath pot; 3) other two ports of the five-necked flask are respectively connected with an inlet and an outlet of a condenser horizontal inner tube, the corrosion coupon is fixed in the condenser horizontal inner tube, a first (I)three-electrode system is fixed in the upper portion of a condenser inclined tube; and 4) the five-necked flask is heated by the numeric display oil bath pot, a first-section condenser outer tube cooling water inlet and a second-section condenser outer tube cooling water outer are opened, the cooling water flow is adjusted, then acidic aqueous electrochemical tests, corrosion weight loss experiments under dew formation environment and electrochemical test experiments under dew formation environment can be performed. The electrochemical test and corrosion weight loss dew point corrosion test are can be performed by the method, tests of electrochemical impedance spectroscopy, electrochemical noise and the like under dew point environment can be realized, and data reliability can be verified by weight loss experiments.