Abstract: A new type of thickness shear (d15) omnidirectional shear horizontal wave (SH wave) piezoelectric transducer was used, and by the combination with the discrete ellipse algorithm,it was employed to detect the damage of the welding joint of the stiffened aluminum plate. Multiple issues, including single damage, multiple damage and damage degree, were analyzed to prove the effectiveness of this technology in identifying damage for the welded structure of stiffened plates, which provided technical support for the application of SH wave in practical engineering.