Objective:To design a specialized ultrasound therapeutic device for rabbit urethral scars and to verify its applicability and effectiveness.Methods:New Zealand male rabbits were used as the experimental objects, and the ultrasound therapeutic instrument was customized according to the structure and size of the rabbit penises. The ultrasound therapeutic instrument included the ultrasound pulse emission and control system, the final-stage amplifier, and the ultrasound probe. Firstly, the ultrasound probe was designed according to the size and structure of rabbit penises, and the parameters of the ultrasound probe were determined by COMSOL finite element simulation and actual testing of the sound field distribution. Secondly, the driving circuit of the ultrasound probe was designed according to the parameters of the elements. Then the ultrasound pulse emission and control system based on the field-programmable gate array (FPGA) and the serial screen were designed. Subsequently, the ultrasound therapeutic instrument was subjected to a performance test and a safety test. The ultrasound therapeutic instrument was constructed to include the ultrasound amplifier and the ultrasound probe. Finally, a rabbit urethra reconstruction model was constructed, and eight white rabbits were randomly divided into a model group and an experimental group. The rabbits in the experimental group received the ultrasound therapeutic instrument for treatment of the urethra immediately, with an ultrasound frequency of 2 MHz, a pulse interval of 10 ms, and an output sound intensity of 0.73 W/cm 2. The treatment was performed twice a week (on Tuesday and Thursday), with 10 min of irradiation each time, lasting for four weeks. The rabbits in the model group did not receive any treatment. The area percentage of transforming growth factor-β1 (TGF-β1), matrix metalloproteinase-2 (MMP-2), and tumor necrosis factor-α (TNF-α) staining-positive areas in rabbit urethral tissues were quantitatively analyzed, and the urethral circumference was calculated using Image J software. Results:Due to the addition of sound-absorbing materials, the sound pressure distribution in the treatment chamber was more uniform, and the average value of the standing wave ratio was 1.11, indicating that the structural design met the design requirements. In the overall performance test, the natural focal position of the three ultrasonic transducers was 10 mm, and the consistency of the sound field distribution meet the experimental requirements. The relationship between the peak sound pressure of each transducer and the power supply voltage was close to linear. The output sound intensity ranged from 0.35 to 0.74 W/cm 2, which met the experimental requirements. With the ultrasound output, the temperature of the test point increased slowly, and this experiment could increase the temperature of the tissue by up to 3.3 ℃, which would not lead to thermal damage to the tissue. Animal experiment results showed that the immunopositive area fraction of TGF-β1 in the urethral tissues of rabbits in the experimental group [(4.21 ± 1.32)%] was smaller than that of the model group [(8.53 ± 3.43)%] ( t = ?4.24, P < 0.001). The immunopositive area fraction of TNF-α in the urethral tissues of rabbits in the experimental group [(5.14 ± 2.72)%] was smaller than that of the model group [(7.23 ± 1.57)%] ( t = ?3.37, P < 0.05). The MMP-2 level in the urethral tissue of rabbits in the experimental group [(10.65 ± 2.24)%] was higher than that of the model group[(6.98 ± 2.74)%] ( t = 2.19, P < 0.05). The urethral circumference [(12 209 ± 2 743) μm] was higher than that of the model group [(10 127 ± 2 237) μm] ( t = 15.46, P < 0.05). Conclusions:An ultrasound therapeutic instrument dedicated to rabbit urethral scars has been successfully designed and can be used for the study of ultrasound treatment of rabbit urethral scars.