The invention discloses a method and device for controlling internal stress of high-strength steel, and the method and the device are applied to a hot rolling flattening machine. The method comprisesthe steps that wavy state information and wavy thickness distribution information of the strip steel in the width direction are obtained; and in the process that the strip steel is flattened through the hot rolling flattening machine, based on the wavy state information and the wavy thickness distribution information, the on-load roll gad shape of the hot rolling flattening machine is corrected inreal time, so that the internal stress of the flattened strip steel in the width direction is uniformly consistent. According to the method and device for controlling the internal stress of the high-strength steel, the technical effect that the internal stress of the high-strength steel in the width direction is uniformly consistent, so that the obvious defect of warping or lateral bending occurring in the subsequent use process is reduced or overcome is achieved.