The invention discloses an external circulation type electrochemical sewage treatment plant deodorization system. The system comprises an odor tank (1), a gas-collecting hood (2), an induced draft fan(3), an absorption reaction tower (4), an electrochemical oxidation unit (5) and a power supply control system (6); a treating method comprises the steps that firstly odor is collected by the gas-collecting hood (2), and then induced into the absorption reaction tower (4) by the induced draft fan (3); an odor absorption zone (406), a baffling mixing zone (407), a regeneration reaction zone (408),a precipitation zone (409) and absorption liquid (410) are arranged inside the odor absorption zone (4); the odor is fully absorbed in the absorption liquid (410), and final oxidation of the odor andregeneration of the adsorption liquid are achieved in the electrochemical oxidation unit (5); sediment and concentrated liquid generated by the absorption reaction tower (4) are periodically discharged from a discharge port (402) and the odor is treated by the absorption liquid and discharged from an air outlet (404). According to the external circulation type electrochemical sewage treatment plant deodorizing system and the method, oxidative removal of odor pollutant components and recycling regeneration of the absorption liquid are simultaneously achieved, thereby saving operating costs.