Abstract: The effects of flap peen on the exfoliation fracture corrosion(EFC) of 7150 alloy had been investigated based on the EFC laws in the blended area of Boeing 737 keel beam lower chord by means of flap peen with different intensity and coverage and the grain aspect observed by SEM.The results show that EFC can be reduced by increasing the coverage or decreasing the intensity.Low grain aspect ratio and compression stress can retard EFC.Within the allowable intensity of flap peen,the process of low intensity and high coverage is an effective process to control and prevent EFC in the blended area of the keel beam lower chord.