The prestress of piezoelectric transducer assembly directly affects the product performance. The large-diameter piezoelectric transducer has higher requirements for prestress control and stress distribution uniformity of piezoelectric ceramics. For the high pre-tightening force assembly of large-diameter piezoelectric transducer, the structure design, assembly method design, and radial stress homogenization of large-diameter piezoelectric transducer were studied. First, a piezoelectric transducer was designed based on the transmission line method and modal analysis. The Morris method was used to analyze the sensitivity of size parameters to the longitudinal vibration frequency, amplitude ratio, and pitch position deviation of the piezoelectric transducer, and piezoelectric transducer with expected performance was designed. Then, a hydraulic tension assembly method was proposed to realize high pre-tightening force assembly of piezoelectric transducer. In order to address the issue of uneven radial stress distribution of piezoelectric ceramics in the process of tensile assembly, the static stress of two key states was analyzed. Finally, a tensile assembly device was designed, and the assembly test of piezoelectric transducer was completed using the device. Results showed that the tensile assembly method could realize the expected performance of piezoelectric transducer assembly. After assembly, the series resonant frequency and parallel resonant frequency of the piezoelectric transducer were stable at 18.05 kHz and 19.57 kHz, the series resonant impedance was within 10 Ω, and the electromechanical coupling coefficient was between 0.34 and 0.36. The research results provide a new method for controlling the prestress of piezoelectric transducer assembly, and offer a solution for the design of large-diameter piezoelectric transducers with uniform ceramic stress.