Abstract: Crack direction recognition is an important part of structural quality monitoring. To solve the problem of detecting different directions of the micro-cracks buried in three-dimensional thin plate structures, a method of numerical simulation is adopted. An improved three-dimensional aluminum plate model including artificial viscoelastic absorbing boundary is established by finite element software ABAQUS. The nonlinear interaction between the S0 mode Lamb wave and the buried micro-crack is investigated. The buried micro-crack is embedded at a fixed position in the plate model. Different micro-crack directions under the same excitation condition are simulated. Fourier frequency spectral analysis is applied to the received signals. Then, the directivity diagrams of the amplitude-ratio of second harmonic to fundamental wave in different crack directions are compared and discussed. Simulation results indicate that cracks in different directions have a distinct effect on the distribution of Lamb wave scattering field in the crack zone; The wave propagation path satisfies the reflection law, and the amplitude ratio of forward-scattering signal is generally larger than that of the back-scattering signal; The artificial absorption boundary can minimize the influence of the reflected wave, and the energies of the fundamental frequency and second harmonic signals become more concentrated and stable; Meanwhile, the amplitude ratio difference between forward-scattering and back-scattering increases with the increase of crack direction angle. The detection results show that the method can identify any crack direction angle within the allowable error range.