Abstract: A line-focusing transducer based on a cylindrical concave structure of 1-3 piezoelectric composite material is designed and developed,which could achieve both a nice line focus and a high bandwidth.Taking the PZT column inside the transducer as an independent sound source,the theoretical expression of the total sound field of the cylindrical concave transducer is derived by applying the Rayleigh integration and superposition principle.The model proposed in this paper is used to calculate the sound field directivity of the transducer in the lateral and side directions.The sound field characteristics of the transducer on the focusing line and the focusing performance affected by transducer parameters are analyzed.Reasonable design of the transducer parameters is proposed to make the focusing line as wide as possible,while keeping a small fluctuation of the focused sound field.It is shown by the experimental test results that the calculated sound field is basically in line with the measured value.It is also shown that the concave transducer forms a clear focusing line in the lateral direction in the vicinity of its geometric focus and the length of the focusing line equals to the lateral length of the transducer.The distribution of sound field fluctuates slightly on the focusing line.