Three-dimensions molecular dynamics (MD) method by employing the embedded atom method (EAM) potential is used to simulate the effect of stress corrosion-induced dealloyed layer existed on the surface of a crack of Cu2Au alloy on dislocation emission and crack propagation. The simulations show that the existence of a dealloyed layer enhances dislocation emission and crack propagation, i.e., decreases the critical stress intensity for dislocation emission from KIe = 0.62 MPam1/2 to KI*e = 0.556 MPam1/2 and that for crack propagating after emitting large amounts of dislocations from KIP = 1.14 MPam1/2 to KIP * = 1.06 MPam1/2. This indicates that dealloyed layer-induced tensile stress can help the applied stress to enhance dislocation emission and crack extension.