The portable inner hole automatic welding is specially designed for on-site construction. It has the characteristic of small volume, light weight, portability and good welding quality. Also, it is with low requirements for service environment and space. It can be used for repairing welding of round holes (such as pin holes) and bearing holes of large equipment. Besides, it is also applicable to inner longitudinal seam welding of short distance. It is a necessary tool for on-site maintenance of industrial and mining enterprises.