Welding joint for friction stir welding

The invention provides a welding joint for friction stir welding. The welding joint for friction stir welding comprises a first welding piece and a second welding piece. The first welding piece and the second welding piece are in butt joint to form an attachment face. A groove with a preset width is formed in the attachment face, a weld seam is formed by the groove, and the preset width of the groove is not smaller than 0.5 mm. According to the welding joint for friction stir welding, the groove with the preset width is formed in the attachment face of the first welding piece and the second welding piece, so that the distance between the two welding pieces does not need to be manually adjusted any more in the assembling process of the welding joint, assembling difficulty is lowered, efficiency is improved, and cost is reduced.