In conventional ultrasonic imaging methods, the specular reflections are usually used for image reconstruction. However, these techniques are not efficient in some cases due to multiple specular reflections, and Mode-Converted acoustic waves. In this study, Mode-Converted Rayleigh wave (MCRW) technique for ultrasonic characterization of defect is presented, where Rayleigh waves traveling along the surface of strong scatterers in the materials are used for reconstruction of inclusions with pitch-catch method. To show the validity of the proposed method, test specimens with various kinds of artificial reflectors, void-like defects, flat-bottom holes are used.