The invention belongs to the technical field of hot rolling and discloses a control method of a width gauge. The method is used for performing controlling when a special-shaped plate blank passes through the width gauge. The method includes the following steps that when a hot-rolled plate blank passes through the width gauge, an outlet lower pinch roll of the width gauge is lifted by 5 mm on the basis of a set position; the pressure of an outlet upper pinch roll of the width gauge is increased by 20% or 30% on the basis of nominal pressure; and after tailing-out of the hot-rolled plate blank is finished, the upper pinch roll is lifted. By means of the method provided by the invention, the passing ability of the special-shaped plate blank in the width gauge can be improved.