In view of the problems of traditional rail submerged arc welding trolley existing in the large-gap submerged arc welding operation of hull curved splice plate, the development requirements of intelligent equipment for large-gap submerged arc welding of hull curved splice plate are proposed, and the railless submerged arc welding trolley is designed in overall structure, software system, and operation flow. The designed railless submerged arc welding trolley can meet the requirements of large-gap submerged arc welding of hull curved splice plate with perfect function and high intelligence.