Abstract: The multi-bolt countersunk single-lap joint of SLM aluminum plate and CFRP composite laminate under tensional load was analyzed via numerical simulation and experiment. Damage initiation and progression in the structure were present in 3D FEM based on the progressive damage analysis (PDA), and the bolt load distributions as well as the failure loads and modes were compared with the physical test. With the consideration of fracture stain to stress triaxiality curve approximated by the author, it is found that there is only 1.9% difference of the failure loads between FEM and test, when both Ductile damage and Hashin criteria are introduced through UMAT. Besides, the failure modes are both pulling out illustrated in FEA and experiment. Consequently, the method assessed in this study has enough accuracy to satisfy the application requirement for such an engineering problem. The progressive damage process of both SLM aluminum plate and CFRP laminate were investigated with the validated FEM and the effect on the failure mode of the joint was studied with different stiffness of SLM aluminum plates. When the thickness of SLM aluminum plate increases to 4 mm, the pulling-out failure mode of the joints transfers from SLM aluminum plate to the CFRP composite laminate.