The utility model relates to a positive-pressure piercing-leakage prevention washing pipe sealing device, which is used for oil and natural gas drilling industry, and comprises an axial oil guide hole (1), an inner high-pressure pipeline (2), a pressurizing cylinder (4), a connecting rod piston (3), a high-pressure oil nozzle (5), an outer high-pressure pipeline (10) and a drilling fluid leading-out hole (11). The area of one end of the connecting rod piston (3) close to a washing pipe (9) is smaller that of the other end of the connecting rod piston (3); an inner cavity of the pressurizing cylinder (4) is divided into an oil chamber (7) and a mud chamber (8); the oil chamber (7) is provided with a check valve (6); the drilling fluid leading-out hole (11) is arranged on the left side of the washing pipe; the axial oil guide hole (1) is connected with the oil chamber (7) by the aid of the inner high-pressure pipeline (2); and the drilling fluid leading-out hole (11) is connected with the mud chamber (8) by the aid of the outer high-pressure pipeline (10). The positive-pressure piercing leakage prevention washing pipe sealing device has the advantages of no need of an external power source, simple use, prevention of drilling fluid intrusion and capability of prolonging the service life of sealing packing.