The invention discloses a horizontal plate shearing machine capable of automatically adjusting a shearing angle and a shearing angle adjusting control method for the horizontal plate shearing machineand belongs to the technical field of forging machine tools. The horizontal plate shearing machine capable of automatically adjusting the shearing angle comprises a rack, a knife rest and a workbench;the rack is internally provided with the knife rest and the workbench which are distributed in a horizontal direction; the workbench is provided with a static knife; the knife rest is provided with amoving knife matched with the static knife; the left side of the rack is provided with a side supporting point; the side supporting point is connected with a rolling wheel through a disc spring; theleft side of the knife rest is correspondingly provided with a guide rail plate; the position, on the inner wall of the rack, of the right side of the knife rest is provided with a first laminating plate and a second laminating plate; and the side supporting point, the first laminating plate and the second laminating plate are provided with a first inductor, a second inductor and a third inductorrespectively. According to the technical scheme of the invention, the shearing angle of the horizontal plate shearing machine can be automatically adjusted, so that the shearing angle is ensured to befixed.