The invention discloses a method and device for controlling radial thickening of the two ends of an internal high-pressure forming three-way pipe. In the forming process of a pipe blank, a lining block is additionally arranged between each pushing head and the pipe blank, and a 45-degree circular bead is chamfered on the butting position of each lining block and the pipe blank. By adopting the lining blocks, the original thickened partial materials on the two ends flow to a bulging area, the phenomenon that the bulging area of the material is thinned is reduced, the phenomenon that the bulgingarea is prone to being broken in the forming process is overcome, forming is easy, the uniformity and size of the wall thickness of the pipe end part of the feeding area are controlled through designof the lining blocks, the fiber flowing direction of the pipe blank material can not be destroyed, and the structure property of the pipe material can not be damaged; and the forming efficiency is improved, the material utilization rate is increased, the subsequent mechanical thinning machining process is reduced, and the machining cost and production investment are reduced.