Ultrasonic Test (UT) is a technique used in industry and science for material evaluation and defect detection. Usually, a liquid coupling agent is applied between the inspection probe and the surface of the inspected workpiece to ensure the inspection performance. In this paper, we propose an ultrasonic dry-coupling inspection method based on multilayer coupling interface to address the problems of complicated operation, high inspection cost and inability to realize automated inspection of the traditional liquid coupling method. We firstly established the reflection and transmission model of ultrasonic waves in the multilayer coupling interface, and secondly, we built an ultrasonic dry-coupling experimental platform, and selected the coupling materials through the acoustic attenuation experiment and acoustic impedance matching experiment. Finally, we carried out dry-coupled ultrasonic detection experiments and compared with the traditional wet-coupled detection method. In the thickness measurement of stepped plate, the maximum detection error was 0.6%, and in the detection experiments of defective plate, the maximum detection error was 5.33%, and the results showed that our dry-coupled detection device has good detection effect.