Due to serve under the environment of high temperature and high humidity, hygroscopic aging behaviors are commonly discovered in adhesively bonded composite repaired metallic aircraft structures, which results in the decrease in mechanical properties and server life. In order to investigate the effect of hygroscopic aging on adhesively bonded composite repaired structures, moisture absorption and aging test were performed on adhesively bonded composite repaired aluminum alloys plates containing double-sides cracks with single patch and E44/Polyamide epoxy resin, then the effect of hygroscopic aging on load carrying capability, crack propagation life, repaired effect and duration of fatigue load were analyzed by the experimental method and finite element method (including damage zone theory and J-integral ). Results show that hygroscopic aging lowers the load carrying capability and fatigue crack propagation life greatly, with the result that the average value of fatigue crack propagation life and ultimate load of repaired structure decreases by 29% and 10% respectively after immersing in water for 40 days, and the failing mode of adhesive changes into interfacial failure from cohesive failure. After immersing in water for 30 days, the adhesive specimens became completely plastic, whose elastic module decreases by 60%, and plastic deformation increases to 25%. The effect of hygroscopic aging on the damage zone was obvious, which results in the fast damage of adhesive, and the longer the crack is, the faster the damage is. The hygroscopic aging of repaired structure also increases the value of J-integral around the crack tips, which decreases the crack propagation life of repaired structures.