The utility model discloses a special hoisting tool for realizing the installation of an underwater wellhead cap without occupying a wellhead, which is characterized by mainly comprising a frame-type body, a loose-leaf type clamping ring and inserting pins, wherein a gap is reserved in the lower frame of the frame-type body, the loose-leaf type clamping ring is spliced into an annular structure by a fixed circular-arc segment and a movable circular-arc segment, the fixed circular-arc segment is arranged at the gap, the positioned surface of the fixed circular-arc segment is vertical to the frame-type body, one end of the movable circular-arc segment is hinged to the frame-type body, a connecting plate is arranged at a position close to the other end of the movable circular-arc segment, pinholes are respectively upwards and downwards correspondingly arranged in the connecting plate and the lower frame of the frame-type body, the joint of the wellhead cap is clamped by the loose-leaf type clamping ring, and the inserting pins are inserted into the pinholes to fix the movable circular-arc segment. The special hoisting tool has the advantages of simplicity in manufacturing and high reliability.