The invention relates to a quality control device for the galvanized surface of a band steel. An early warning removing device for sticking zinc of a sink roll which includes a motor, an air cylinder (1), a set of device which can warn early and can control a scarper (6) to scrap zinc as well as a zinc liquid slot (4) the upward side of which is provided with a transversely arranged walking beam 3; the zinc liquid used for galvanizing and a transversely arranged sink roll (5) are arranged in the slot; the walking beam is connected with the scraper with a tool arm (61); the connection positionof the tool arm of the scraper and a scraper body (62) is connected with the walking beam and can move along the walking beam transversely under the driving of the motor; the front end of the scraperbody of the scraper is arranged in the zinc liquid slot; a scraper edge can contact the surface of the sink roll; the piston rod of the air cylinder is connected with the tool arm of the scraper usedfor adjusting the pressure of the scraper to the sink roll; the body of the air cylinder is provided with a displacement sensor (7) used for monitoring the movement of the tool arm of the scraper. The signal of the sensor is used for warning early and scrapping zinc.