The invention relates to a safe righting device of a heavy type assembling machine. According to the technical proposal provided by the invention, the safe righting device of the heavy type assembling machine comprises a drive motor and a speed reducer which are fixedly arranged on a material pressure rack; the speed reducer is provided with output shafts transversely extending to the left side and the right side of the speed reducer; the end parts of the output shafts of the speed reducer are connected with screw rods; the material pressure rack corresponding to the screw rods at the two sides is connected with a movable rack transversely in a sliding mode; the movable rack is fixedly provided with nuts screwed with the screw rods; the movable rack is connected with righting arms extending downwards; the bottom end part of the righting arm on the left side is connected with a supporting arm transversely extending rightwards; the bottom end part of the righting arm on the right side is connected with a supporting arm transversely extending leftwards; and the right end part of the supporting arm on the left side and the left end part of the supporting arm on the right side are rotatably connected with an idler wheel respectively. The safe righting device has the advantages of improving the production efficiency, lightening the labor intensity of laborers, increasing the operating safety of the laborers and the like.