The invention discloses a small radius forming tool for a large-diameter guide tube. The small radius forming tool for the large-diameter guide tube comprises a bending mold and a clamping block, wherein the bending mold comprises a forming mold (1), a first clamping mold (2) and a second clamping mold (3). Both the first clamping mold (2) and the second clamping mold (3) are connected to the forming mold (1) to form an integrated structure; a first groove structure (4) is arranged on the outer surfaces of the forming mold (1), the first clamping mold (2) and the second clamping mold (3); and an auxiliary clamping mechanism (5) is fixedly connected to the upper side of the first clamping mold (2). The small radius forming tool for the large-diameter guide tube is used for numerically controlled brake forming of the guide tube, so that the machining efficiency and quality are improved; the deviation value between the formed guide tube and a theoretical shape is reduced to meet a specified value; a tubular product is not scrapped, the repair rate is zero, and the machining quality is greatly enhanced.