The invention discloses a weld-assembled ladder which comprises ladder protection heads, cross beams, upper sides, fixed plates, hinged support plates, hinge plates, gaskets, supporting plates, lower sides, long cross beams and sealing plates. The ladder protection heads are arranged at the tops of the upper sides, and the two upper sides are connected through the cross beams. The two fixed plates are arranged at the lower portions of the lower sides, the hinged support plates are arranged at the bottoms of the upper sides, and the hinge plates are arranged at the bottoms of the hinged support seats. The hinge plates in the upper sides and the hinge plates arranged at the tops of the lower sides are connected through bolts, each gasket is arranged between every two corresponding hinge plates, the two lower sides are connected through the long cross beams, and the sealing plates are arranged at the positions, at rod bodies at the two ends of the long cross beams, of the lower sides. Through the welding technology and close coordination of all the components, the ladder is stable in work property, no shaking phenomenon occurs, and meanwhile the ladder is simple in structure and reasonable in design.