The utility model discloses a band steel water stain blowing device of a continuous annealing unit, which is arranged between a sandwich iron plate above a water quenching tank and an air bellows, and comprises two compressed air blowing mechanisms symmetrically arranged, wherein each blowing mechanism consists of a bracket, a blowing component and a translation driving component; and the blowing component is arranged on the bracket, and the translation driving component is arranged on the bracket and connected with the blowing component. By adjusting the extending amount and swing angle of a nozzle, the most proper distance and angle of the blowing device and the surface of the band steel can be formed, so that effective blowing and clearing can be conducted to the water stain on the surface of the quenched band steel, and the quality of the surface of the band steel can be ensured.