The invention discloses an anti-deformation correcting process of a rod portion of an arm body of an automotive brake adjusting arm by thermal treatment. The process comprises the following steps: heating a workpiece to 580-620 DEG C, putting the workpiece in an ice bucket for 3-4s, taking out the workpiece and putting the workpiece in a mold, the middle of which is suspended, starting a hydraulicdevice, applying a pressure to the reverse direction of deformation of the rod portion of the arm body of the automotive brake adjusting arm, wherein the deformation is smaller than 3mm, the distanceof pressing the workpiece by the hydraulic device at one time exceeds 1/3 deformation of the horizontal plane, the deformation exceeds 3mm, the distance of pressing the workpiece by the hydraulic device at the last time exceeds 1/3 deformation of the horizontal plane in multiple pressures applied by the hydraulic device, and the pressing speed of the hydraulic device is 6-8cm/min; and quickly putting the workpiece in two plates, starting the 100-ton hydraulic device, applying pressures to the plates, and naturally cooling the workpiece. As a high-temperature tempering method is not adopted, the process disclosed by the invention is simple and practical, the deformation error of the workpiece caused by thermal treatment can be reduced remarkably, and the mechanical property of the workpiece is not reduced, and the correcting effect is guaranteed.