Control method of reducing finish rolling scratch defects of thick plate

The invention discloses a control method of reducing finish rolling scratch defects of a thick plate. According to the control method of reducing finish rolling scratch defects of the thick plate, ina strip steel throwing process among racks of a finish rolling unit, when a loop is switched from a small looping mode when the front rack is prepared to throw steel to a waiting position mode, supporting torque compensation to the tail part of the steel strip by the loop is increased, so that the scratch defects of the lower surface of the steel strip as the loop angle falls too low when steel isthrown are avoided. When the loop is switched from the small looping mode to the waiting position mode, supporting torque compensation to the tail part of the steel strip by the loop is increased, the loop angle is prevented from being pushed too low by the tail part of the steel strip, and the scratch defects of the lower surface of the steel strip as the loop angle falls too low are avoided during APC control of the loo