The invention discloses a soluble tail tube plug and belongs to the technical field of under-pressure well workover of oil-gas wells and completion underground tools. The soluble tail tube plug comprises a plug body, a plugging sub and a plugging part; the lower portion of the plug body is fixedly connected with the upper portion of the plugging sub; both the upper portion of the plug body and thelower portion of the plugging sub are connected to a string; the peripheral edge of the plugging part is embedded in the part, connected with the plugging sub, of the plug body. The plugging part includes a separator portion, a fixing portion and a shearing portion to connect the separator portion and the fixing portion; the fixing portion is connected with the plug body and the plugging sub to fix the plugging part; the shearing portion is arranged close to the tubular wall of the plug body; the thickness of the shearing portion is less than that of the separator portion; the plugging part is made with soluble aluminum alloy. The soluble tail tube plug has the advantages that the plug herein can be effectively broken; smoothness in a tube is optimized; the problem of residual breakage inthe string is solve; the blocking and other problems are avoided; formation pollution can be maximally reduced; reservoirs are protected.