The invention discloses a leak-proof device for a prestress concrete hollow pipe pile cap. A prestress concrete hollow pipe pile comprises a pipe pile body in a hollow pipe shape, and a pile cap arranged at the upper end of the pipe pile body, wherein the pipe pile body is vertically arranged. The leak-proof device comprises a disc-shaped tray, a water-expandable rubber ring arranged around an outer ring of the tray, and a connecting part, wherein one end of the connecting part is fixedly connected with the tray, and the other end of the connecting part is hung to the upper end of the pipe pile body. As the water-expandable rubber ring is arranged on the outer ring of the tray, after the tray and the water-expandable rubber ring are placed into the pipe pile body, watering is carried out to enable the water-expandable rubber ring to be expanded so that all gaps between the tray and the inner wall of the pipe pile body can be blocked completely, and slurry leakage can be effectively prevented.