The invention relates to the technical field of earthing in a direct current power transmission project, and discloses a connecting piece, a deep well type vertical earthing electrode, and an assemblymethod of the deep well type vertical earthing electrode, which aim to solve the problem of how to improve the welding strength and reliability between a feed steel pipe and a current guiding cable in the deep well type vertical earthing electrode. The connecting piece comprises a lantern ring, and a connecting lug fixed on the outer wall of the lantern ring, wherein the lantern ring is used to be in sleeve joint with the feed steel pipe in an interference fit manner; and the connecting lug is used to be welded with a conductor in the current guiding cable. The connecting piece disclosed by the invention is used for connecting the feed steel pipe and the current guiding cable.