Abstract: In order to reduce the influence of various noise interferences on the extraction of lap weld feature information,an acoustic sensor for detection of lap weld deviation was designed. The sensor is mainly composed of two microphones and a sonic emitter, which can identify the position of the weld based on the difference between the left and right microphones. The three-dimensional model of the sensor was established by using LMS Virtual.Lab Acoustics software and the numerical simulation analysis on the internal sound field of the sensor was performed, the frequency response of the sensor and its sound transmission loss were analyzed. The research results show that the sensor has a better frequency response in the high frequency range, and the sensor can accurately detect the offset distance of the weld. The best excitation frequency for the detection of weld position is 17001 Hz. It proves the feasibility of the acoustic sensor designed for detecting lap weld deviation in the welding seam position detection.