The utility model belongs to the field of corrosion prevention and pollution prevention, and relates to a device for measuring the damage rate of a coating on the inner wall of a pipeline, which is used together with an impressed current cathodic protection system and comprises a flange plate (1), an electrode probe (2), a flange base (3) welded on the pipeline and a potentiostat (8), wherein theflange plate (1) bears the electrode probe (2) and is connected and sealed with the flange base (3) through a bolt; the electrode probe (2) aims to acquire a current signal flowing through the device,and the current is combined with the output current of a pipeline cathode protection system, so that the damage rate of the coating on the inner wall of the pipeline can be calculated. The device canmonitor and measure the damage condition of the coating on the inner wall of the pipeline additionally provided with the cathodic protection anti-corrosion system on line and measure the damage rateof the coating on the inner surface, is convenient to install, does not need to be replaced, can monitor on line, and is simple in method, and the calculation result is well matched with the actual condition.