Abstract: Semi-elliptical surface cracks are one of the most frequent cracks found in many structures in service, such as off-shore structures and aircraft components. The expense of replacement and time out of service have made repairing policy more attractive. Use of bonded composite patches is widely regarded as favorite reinforcement methods for repairing cracked structures. It is the main aim of present work to investigate the effect of the single-sided composite patch on residual strength of a semi-elliptical surface crack. Computer code ANSYS is used to calculate numerically the stress intensity factor of rehabilitated cracks. The influence of geometrical and mechanical parameters has been studied and it is found that the presence of composite patch leads to a massive reduction of stress intensity factor along crack front. Moreover, the stress intensity factors remain almost unchanged for different crack width and depth when rehabilitated with composite patches.