The invention discloses a full-automatic welding system of an electromagnetic assembly of a low-voltage circuit breaker. The system comprises a rotary disc arranged on a horizontal table top. Eight clamp assemblies are uniformly arranged along the circumference close to the outer edge of the rotary disc, and an indexing mechanism is arranged on the lower surface of the rotary disc; eight mechanisms are successively arranged around the periphery of rotary disc on the horizontal table top; the eight clamp assemblies are uniformly distributed as eight rotating stations which are successively an oil cup loading station, a lower gasket loading station, a magnet yoke loading and storing station, a coil loading station, an upper gasket loading station, a magnet yoke loading station, a tin solder station and a discharging station. A product taking mechanism is arranged on the outer side of the discharging station. The invention also discloses a welding method of the electromagnetic assembly of the low-voltage circuit breaker. The device and method disclosed by the invention are compact in structure, reliable to work and high in welding quality.