Abstract: The extended finite element method(XFEM) and cohesive zone model(CZM) were combined to investigate the adhesive layer of scarf-repaired laminates, which could describe the debonding between composite and adhesive layer and the crack propagation in the adhesive at the same time. The numerical strength shows good agreement with test results. Both the interface defect and inner defect were taken into consideration, the influences of defect length and defect location were analyzed. The results indicate that the structure with inner defect is more dangerous than that with interface defect under the same condition. The structure strength which is influenced by both the defect length and the ply orientation near the defect tip decreases with the increased defect length. And the decrease rate is larger than the increase rate of defect length. When the defect location changes, the structure strength is mainly associated with the average shear stress level of adhesive layer at corresponding region. At last, parameter study was performed to investigate the influence of the interface shear strength.