The work aims to investigate the effects of micro-defects on deformation behavior and failure mechanism of high temperature coating B2-NiAl under uniaxial tensile load. In consideration of micro-defects like cracks, voids, etc., EAM and molecular dynamics were used to simulate the failure process of B2-NiAl coating without defects (sample 1), B2-NiAl coating with central symmetric micro-crack (sample 2), B2-NiAl coating with central micro-crack and single void (sample 3) and B2-NiAl coating with central micro-crack and double voids (sample 4). The common neighbor analysis (CNA), centrosymmetric parameter method (CSP) and radial distribution function (RDF) were used to analyze and characterize the failure process and mechanism of B2-NiAl. With the increase of micro-defects, the yield stress, Young’s modulus and yield strain decreased, while the second yielding phenomena appeared due to the existence of micro voids in the tension process. The dislocation and phase transformation area of B2-NiAl high temperature coating without defects became smaller after the yielding, but were distributed evenly. The crack would extend along the (100) direction first and then the (111) direction until failure. Compared with the perfect B2-NiAl high temperature coating, the dislocation and phase transformation area of B2-NiAl coating with micro cracks and voids became smaller after the yielding and were mainly distributed along the sliding direction of crack tip <111>. The crack only extended along the [100] until failure. In addition, micro crack can decrease the strength of B2-NiAl, but micro void can improve the plasticity. Stress concentration caused by dislocation stack can lead to micro cracks and micro voids near the crack tip to connect the main crack until the failure.