Abstract: When there are microcracks inside the tungsten carbide, it will affect its service life. Lamb waves are often used for nonlinear ultrasonic nondestructive testing, and they are widely used in the detection of microcracks in aluminum plates, but for tungsten carbide, due to its large absorption coefficient, the nonlinear effect is not obvious enough. Therefore, this paper studies the methods of increasing the nonlinear coefficient interaction between Lamb waves and tungsten carbide and the method of locating microcracks, and achieves microcrack detection of tungsten carbide based on ultrasonic Lamb waves. A three-dimensional detection model of tungsten carbide plate is established using the COMSOL Multiphysics simulation software, and the simulation experiments of microcrack length and width are carried out. The experimental results show that the nonlinear coefficient increases as the length of the microcrack becomes longer and decreases as the width of the microcrack becomes wider. The smallest carbide micro-crack that can be detected is 0.2mm in length and 0.04um in width, and the positioning error is within 2mm.