The present invention relates to a mesoscale elastic thin-walled workpiece deformation on-line prediction and compensation method and belongs to the machining field. The mesoscale elastic thin-walled workpiece deformation on-line prediction and compensation method is realized by a machine turntable, a dynamometer, a driver, a controller, a cooler, a bracket, a fine milling cutter, an infrared thermal imaging instrument and an adjustment mechanism for compensating radial immersion. With the mesoscale elastic thin-walled workpiece deformation on-line prediction and compensation method of the invention adopted, the deformation condition of a processed thin-walled workpiece can be monitored online in real time; the adjustment mechanism controls a screw and a screw-nut pair to adjust a supporting table in real time, so that radial undercut caused by the deformation of the workpiece can be eliminated, and therefore, machining precision and quality can be improved; and the adjustment mechanism is independent of a machine tool control system and will not affect a tool path planned by an existing program, and therefore, programming efficiency can be greatly increased, and production efficiency can be improved.