The invention discloses a large mass plug gauge lifting device and an online adjusting method thereof. The large mass plug gauge lifting device comprises a arch hanger rod, a left-hand and right-handthread stud, a special nut, a nut, a sleeve retaining assembly, a circular ring, a connecting block, and a lifting ring; the arch hanger rod is divided into three parts, an upper part is an inclined section, a lower part is a horizontal section; the horizontal section of the arch hanger rod is a step shaft, the small diameter section of the the arch hanger rod is provided with the circular ring, the circular ring is arranged in a circular arc annular groove of a plug gauge inner hole; the upper section of the inclined section of the arch hanger rod is a threaded section, the special nut is screwed on the threaded section through an axial threaded hole, the lower end of the left-hand and right-hand thread stud is connected with the large threaded hole of the special nut, the upper end of the left-hand and right-hand thread stud is connected with the threaded hole of the connecting block; the rotation directions of the threads of the two ends of the left-hand and right-hand thread stud are opposite, and one end is left-handed and one end is right-handed. According to the large mass plug gauge lifting device and the online adjusting method thereof, the adjustment of six degrees of freedom such as three translation and three rotation of the large mass plug gauge can be conveniently realized, so that the method and technology of the plug gauge inspection are applied in the inspection of the hole structure of heavy machinery parts.