Ram is a very important component of super-heavy-duty computer numerical control (CNC) floor type boring-milling machine, and deformation of ram is a significant source causing errors in machining process. To compensate the deformation error of super-heavy-duty CNC floor type boring-milling machine, based on force analysis theory, the law and compensation measures of deformation of ram are researched. Based on the principle of torque (force) balance of the ram components, the formulas of compensation forces and compensation torques are derived, the relations between compensation forces (compensation torques) and the stroke distance of the ram are given. According to theoretical analysis results and the structural characteristics of super-heavy-duty CNC floor type boring and milling machine of TK6932, rods compensation, hydrostatic pressure compensation and wire rope compensation measures are taken to compensate the deformation error of ram. The experiments and computer simulation results show that the straightness of the ram at its overhanging end meets the national machinery industry standards. Ram is a very important component of super-heavy-duty computer numerical control (CNC) floor type boring-milling machine, and deformation of ram is a significant source causing corner in errors in machining process. To compensate the deformation error of super-heavy-duty Based floor-boring-milling machine, based on force analysis theory, the law and compensation measures of deformation of ram are researched. Based on the principle of torque (force) balance of the ram components, the formulas of compensation forces and compensation torques are derived, the relations between compensation forces (compensation torques) and the stroke characteristics of super-heavy-duty CNC floor type boring and milling machine of TK6932, rods compensation, hydrostatic pressure compensation and wire rope compensation measures are to compensate the deformation error of ram. The experiments and computer simulation resul ts show that the straightness of the ram at its overhanging end meets the national machinery industry standards.