In　this　paper,　three-dimensional　finite-element　modeling　is　conducted　to　investigate　the　nonlinear　interactions　between　Lamb　waves　and　microcracks.　The　simulation　research　focuses　on　the　influence　of　microcrack　orientation　on　the　propagation　direction　of　generated　sum-frequency　Lamb　waves.　The　simulation　results　show　that　the　resonant　conditions　based　on　classical　nonlinear　theory　are　valid　for　such　interactions,　leading　to　the　generation　of　transmitted　and　reflected　sum-frequency　S0　waves　(SFSWs).　Moreover,　the　propagation　directions　of　these　two　SFSWs　exhibit　different　trends　with　respect　to　the　orientations　of　microcracks.　The　transmitted　SFSW　can　be　used　to　detect　microcracks,　whereas　the　reflected　one　can　be　used　to　measure　their　orientations.