The invention provides a welding-mounting system and welding method for a low-voltage circuit breaker electromagnetic coil assembly. An outer rotary table of the welding-mounting system is provided with a fixed contact feeding gear, a wiring board feeding gear, a fixed contact detecting gear, a wiring board detecting gear, a coil feeding gear, a coil detecting gear, a fixed contact welding gear, a first welding point detecting and finishing gear, a wiring board welding gear, a second welding point detecting and finishing gear, a discharging gear and a finished product blanking detecting gear. A fixed contact clamping detector, a wiring board clamping detector, a coil clamping detector, a fixed contact welding mechanism and welding wire feeding mechanism, a fixed contact and coil welding-forming detector and finishing mechanism, a wiring board welding mechanism and welding wire feeding mechanism, a wiring board and coil welding-forming detector and finishing mechanism, a finished product detector and a blanking detector are arranged on a vertical plate. The vertical plate, the outer rotary table, a locking device and the welding mechanisms are combined together, a plurality of coil assembly bodies are manufactured simultaneously, and the welded coil assembly is high in quality.