Abstract: To study the transient characteristics of the sound field of the piezoelectric ultrasonic internal detector probe array, a finite element model of the probe array in the pipeline was established by COMSOL Multiphysics software, and the correctness was verified under experimental test conditions of the self-developed piezoelectric ultrasonic internal detector. Transient characteristics of the sound field under working conditions of single probe and double probes were studied respectively, and the variation of sound pressure at each point of the sound field under the two working conditions was obtained. The results show that the influence of echo signals on the signal reception of adjacent probes is small. When two adjacent probes work at the same time, the sound pressure superposition area is far away from the probe surface, and its influence on signal reception of adjacent probes can be easily eliminated. This model can determine the total sound field of a probe array in the pipeline under given conditions, and provide theoretical basis for the design of the piezoelectric ultrasonic internal detector.