Abstract: Among the available underwater pipeline repair methods, hyperbaric TIG welding technology may be the easier one to obtain better joint quality.Due to the low automation level and the bevel preparation difficulty, the repair welding should be conducted based on both the welding knowledge of the welder on deck and the operation skill of the diver.A tele-operated robot for all position hyperbaric pipe welding was developed.In the specified case of underwater welding, the process was controlled by a surface based operator, a clear and real time image of the arc as well as the image of groove location were required.An observation system of three cameras for chamber, groove and weld was also developed respectively.All the necessary message of vision, welding current and arc voltage were collected and transferred to the surface by the developed computerized information system.The underwater pipeline maintanence system consists of the welding robot, observation system, the information system, together with the habitation.The chamber gas type, the welding power source and arc striking were also studied.With the welding proceedure developed in the hyperbaric welding laboratory, a good weld was obtained in a underwater pipe repair welding test at Bohai sea.