Abstract: Based on the spherical zone cavity focused ultrasound transducer, a partial spherical crown focusing ultrasound transducer with C-shaped vertical segment is designed to study the influence of its structural parameters on the shape of acoustic focal region. Through the established finite element simulation model, the relationships of the spherical zone height and the focused angle of the transducer with the shape of focal region are discussed. The results show that the higher the spherical zone height and the larger the focused angle, the smaller the focal region size, the lower the ratio of long axis to short axis of the focal region, so that the focal region tends to be round; especially when the spherical zone height is 1.6 focal length and the focused angle ≥ 210°, the triaxial dimension of the focal region can all reach the sub-wavelength scale. In order to verify the correctness of the simulation results, a transducer that can change the focused angle is designed and tested. The experimental results are in agreement with the simulation results. Compared with the traditional travelling wave transducer, the designed transducer can improve the shape of focal region obviously, compress the ratio of long axis to short axis of the focal region and improve the focused accuracy effectively, which provides a design method of improving the focal region shape of the focused ultrasound transducer.