Edge waves in a three-dimensional plate are considered as the singularity cases of the obliquely incident and reflection fields of Lamb modes and horizontally polarized shear (SH) modes, solved by mode matching based on a real orthogonal relation or the boundary collocation technique. With that, the dispersion curves of the edge waves in a duralumin plate are evaluated. The leaky edge waves are predicted and the one corresponding to quasi-resonance at free-edge in a plane strain plate are verified together with the pure edge waves. The high-frequency features of the dispersion curves are discussed.