Abstract: Radiated filed from a self-focusing ultrasonic piezoelectric transducer with a truncated cone shape is calculated Influence of the geometric parameters b (radius of the small section),a (radius of the large section),and h (height) on the acoustic field of the axis and the focal plane is discussed The results show that distribution of the axial acoustic field is undulated with relatively high average sound intensity There exists a set of optimal parameters,leading to the best focusing effect with even distribution of transverses acoustic field,a small effective radius of focal plane,and less sensitivity to the choice of geometric parameters.