The utility model provides a drilling water supply pressurization device of a karst development area underwater pile foundation, which solves the problem that an existing karst development area underwater pile foundation descends and is prone to cause hole collapse and drill burying. The drilling water supply pressurization device of the karst development area underwater pile foundation comprises a pile casing. At least one water inlet is arranged on the lateral wall at the lower portion of the pile casing, a retaining board covered on the water inlet is hinged on the pile casing above the water inlet, and a balancing weight is suspended at the lower end of the retaining board. A winch is arranged above the pile casing, and a steel wire rope connected with the winch and the retaining board is arranged between the winch and the outer surface of the retaining board. The drilling water supply pressurization device of the karst development area underwater pile foundation is reasonable and reliable in structural design and capable of timely raising the liquid surface in a drill hole by arranging holes and the retaining board on the underwater pile casing so as to ensure the balance between the inner pressure and the outer pressure of the drill hole, improve stability of the lateral wall of the drill hole and reduce loss caused by sudden descending of the liquid surface of slurry.