The invention discloses a welding method of the intersection of a rib plate of a locating arm. Three plates welded perpendicularly are included. The welding position of the first plate and the secondplate is named as a first corner joint. The two welding positions formed by at least two adjacent faces of the second plate and the third plate are named as a second corner joint and a fourth corner joint. The welding position of the third plate and the first plate is named as a third corner joint. A first corner joint weld bead, a second corner joint weld bead and a third corner joint weld bead intersect at one point. The method comprises the following steps that firstly, the first plate, the second plate and the third plate are assembled; 2, the third angle joint weld bead is welded; and thirdly, a fourth corner joint weld bead, the second corner joint weld bead and the first corner joint weld bead are welded in sequence, a semi-n-shaped track welding method is adopted, and one-time welding is achieved. By means of the method, the number of the joint at the intersection is reduced to one from three, welding defects are reduced, the inner quality is obviously improved, and the phenomenon that an end socket is not welded due to a thick arcing point is avoided.