The invention belongs to the technical field of steel for board ship structures, and provides a secondary descaling method for improving surface quality of ship boards. The secondary descaling method is applied to secondary descaling of a double-machine-frame heavy and medium plate mill in the rolling process. Different descaling passes are selected for the ship boards of different specifications and different process routes. The descaling passes for secondary descaling are reasonably selected, so that scale structures of the surfaces of the ship boards are controlled, defects of the surface of a steel plate are reduced, and the aim of improving surface quality of the ship boards is achieved. The secondary descaling method has the advantages of improving the surface quality of a rolled steel plate to the maximum extent and improving compactness and homogeneity of scale. By means of implement of the operation method, the surface quality of the ship boards is greatly improved, the requirement of a ship owner and a shipyard for the surface quality is met, further processing of the shipyard is reduced, and cost is reduced.