A device using the live welding method for aluminum electrolytic cell overhauling under series full current consists of short-circuit buses at the bottom of the cell (1), pillar buses (2), an anode bus (3), a balance bus (4), a inter-cell standby bus (5), a door-shaped pillar clamp (6), an arcuate clamp (7) of anode buses, a current conversion switch (8, a mechanical switching device (9) for the short-circuit port, a voltage sensor and wires thereof (10), a temperature sensor and wires thereof (11), a system (12) for data acquiring, displaying, analyzing and alarming, an A-side welding area (13), a B-side welding area (14) and compression-joint points (15) on pillar soft belts of overhauling cells; and the live welding method comprises the following steps: when welding is required to be performed in some zone, the currents of short-circuit buses at the bottom of the cell (1) and pillar buses (2) which influence the welding area most are cut off, the serial currents are shunted to other pillar buses (2), other buses at the bottom of the cell (1) and the inter-cell standby buses (5) such that the magnetic field intensity at the welding area can be lowered to the extent that welding can be performed so as to perform welding, and such a device and method can achieve live welding of aluminum electrolytic cells overhauling under series full current.