The invention relates to the field of ship manufacturing tooling, in particular to a codeless assembling and welding pressing device for ship butt seams. The codeless assembling and welding pressing device for the ship butt seams is used for pressing and fixing two to-be-welded welded plates and comprises a jacking and supporting structure, a pressing plate crossbeam structure, a portal frame walking mechanism and a hydraulic lifting mechanism; wherein the jacking and supporting structure is used for supporting and fixing the welded plates from the bottom; the pressing plate crossbeam structure is used for pressing and fixing the welded plates from the upper part; and the portal frame walking mechanism and the hydraulic lifting mechanism are used for lifting and controlling the pressing plate crossbeam structure. According to the codeless assembling and welding pressing device for the ship butt seams, the horizontal welded seams of a jig frame bed board can be positioned and assembledquickly, welding and code clamping are not needed in the processes of welding and assembling, code feet are not left after welding is completed, the construction efficiency of a jig frame jointed board is high, the process is reduced, the consumed cost of butt seam construction of a plane segment is reduced, and the production efficiency and welding quality are improved.