The invention provides a full-automatic underwater welding method and equipment. The equipment comprises an air compressor (1), a gas cylinder (2), a welding camera (3), a welding test chamber (4), a water drain device (5), a hydraulically-driven automatic welding platform (6), a water surface (7), a welding analyzer (8), a welding power supply (9), a monitoring television cabinet (10), a control system cabinet (11), and a manual control box (12). A local dry underwater welding method is used for underwater surfacing and groove butt welding; during welding, the unitary pulse metal inert gas arc welding is adopted; the gas used for water drainage during the welding is also used as the welding shielding gas; before welding, the welding parameters including welding method, welding speed, swinging speed, swinging amplitude, left-right standstill time and the like are set through the manual control box (12) as required, wherein the parameters can be regulated in real time according to the actual condition; the camera system is used for performing omnibearing remote monitoring on the inside of the welding test chamber (4); and the welding analyzer (8) is used for acquiring welding electric parameters and performing statistical analysis in real time. The equipment can be used in the places where the personnel cannot reach, such as deep water area, radiant environment and the like, thereby not only realizing remote control of fully-automatic underwater welding operation, but also ensuring good formation of seams to further ensure the obtaining of high-quality underwater welding joint.