The invention discloses a waterproof structure of a piezoelectric ultrasonic transducer, which comprises a cylindrical shell. One end of the shell is provided with a shell cap, and the other end of the shell is provided with an acoustic wedge; a piezoelectric wafer is arranged between the acoustic wedge and the shell cap. The waterproof structure is characterized in that: a first sealing device is arranged between the inner end face of the shell and the end face of the acoustic wedge; and a second sealing device is arranged between the inner surface of the shell and the peripheral wall of theacoustic wedge. The waterproof structure of the piezoelectric ultrasonic transducer has the advantages of realizing multiple seal in different directions, improving sealing performance, and achievingcompletely waterproof effect even under high water pressure.