Abstract: A new type of ultrasonic guided wave array transducer was proposed and developed for the detection of thick walled pipelines.The characteristics of the transducer were narrow-beam and concentrated-energy. Firstly, the guided wave mode which was sensitive to the defects both on the outside and inside surface of thick wall pipe, and the incident angle and frequency, were selected. Then, the finite element simulation and optimizationof sound field were proposed for this transducer with 0.5-1.0 wave length pitch and 4-8 elements. The optimum number of array elements and pitch were selected. Finally, a transducer was made and the sound field was measured by experiment. The experiment result shows that compared to the traditional single element transducer, the directivity and energy of narrow beam array transducer (NBAT) are more concentrated.