Abstract: Based on experimental study, damage propagation and ultimate strength of the scarf repaired composite laminate were analyzed through a 3-D FEM (Finite Element Method) damage accumulation model, and the influence of scarf angles on structural tensile performance was discussed. Numerical results match well with experimental results. It is shown that damage occurs firstly in adhesive near 0° ply ends in the center of the whole structure, then damage grows gradually, finally, when about 40% of the adhesive is damaged, a significant decrease is observed in the stiffness of the scarf repaired composite laminate, and the adhesive becomes invalid; Before damage in adhesive occurs, some damage in parent plates and patchs has been observed, which propagates along the bondline of laminate and adhesive before the adhesive becomes totally invalid, then it quickly reaches to the free edge along the narrowest part of the parent plate; Damage propagation in adhesive stops after the adhesive is invalid. The ultimate strength of adhesive decreases as the scarf angle increases, on the other hand, a larger scarf angle results in a longer damage propagation path in parent plate, which benefis the ultimate strength. Therefore in engineering practice, the scarf angle should be decided by structural requirements, production process and other factors.