To investigate the effects of sustained load on bonding properties of CFRP (Carbon Fiber Reinforced Polymer)-concrete interface, the ultimate debonding load of interface P_u was determined by three double shear specimens, and twenty-four double shear tests were performed under four load levels and four duration days of 5, 10, 15, 30, 60 and 90 for each load level. Results indicated that the interfacial slip s₀ corresponding to the peak interfacial shear stress τ_max was reduced under sustained load, but reduction magnitude shows an un-notable correlation with the duration and amplitude of load. The slip s₀ reduces by about 50% after the load duration for ninety days. When the load is greater than 0.5P_u, the peak shear stress τ_max closed to loading position ranging of 15 mm decrease with the increase of load level and duration, but exhibit un-notable changes in other position. Finally, the bond slip constitutive model of CFRP-concrete interface under sustained load was proposed based on these test data. The failure test showed that there was no significant effect of sustained load on the ultimate debonding load when the bonding length is greater than the effective bonding length, but the peeling load P_db of interface during the first stripping in the debonding process was reduced due to the sustained load. When the loads of 0.5 P_u, 0.7 P_u, 0.9 P_u last for 90 days, the peeling loads P_db reduce by 42%, 54%, 66% respectively.