The invention relates to a belt running deflection preventing and deflection rectifying device for an electronic belt scale, and belongs to the technical field of electronic belt scales. The device comprises a sliding base, a tensioning carrier roller, a fixed carrier roller, an electric push rod, a detection switch support, a detection switch, pressure sensors and knuckle bearings. The two ends of the tensioning carrier roller and the two ends of the fixed carrier roller are supported on the sliding base, each of the two ends of the tensioning carrier roller is provided with one knuckle bearing and one pressure sensor, one end of the tensioning carrier roller is connected with the corresponding knuckle bearing and the corresponding pressure sensor, fixing is achieved after pre-tightening, and the other end of the tensioning carrier roller is connected with the corresponding knuckle bearing, the corresponding pressure sensor and the electric push rod; the tensioning carrier roller is pushed and pulled by the electric push rod to slide in a sliding groove of the sliding base; balance of force of the two sides of a belt is detected through a force measuring element, and through adjustment of an execution element, the effect of preventing running deflection is achieved; and meanwhile, during debugging, automatic deflection rectifying is achieved, the belt runs according to the correct position, and the device is reliable and stable, simple in structure and convenient to maintain.