The invention relates to a submerged arc surfacing welding method of an L-shaped groove of a shell flange. The submerged arc surfacing welding method disclosed by the invention aims at establishing a novel welding technology method for the welding of the shell flange which is a key component of a main pump motor, and the problems that the uneven distribution of a magnetic field is caused by a local special structure form of a shell flange product piece, the arc stability is affected, and the generation of air-hole-shaped defects is easily caused on a surfacing welding bead surface can be effectively overcome by adopting a new welding sequence, a welding bead arranging method and the dwell time of mechanical swing, thus the welding quality can be increased, and structural design requirements can be met; and the submerged arc surfacing welding method disclosed by the invention has a higher application value on engineering and has a far-reaching social significance.