In order to study the bond performance between GFRP bar and marine concrete under sustained load,16 GFRP bar-marine concrete beam specimens were designed and fab-ricated.The 120-day sustained load test was carried out under different sustained load levels(0%Pu,25%Pu,45%Pu and 65%Pu).The instantaneous slip and time-varying slip be-tween GFRP bar and marine concrete during the loading process were analyzed,and the time-varying slip models under different load levels were established.The size and variation of the slip between GFRP bar and concrete and of the slip between ordinary rebar and con-crete under continuous load were compared and analyzed.The test results show that the in-stantaneous slip increases with the increase of sustained load level,and the slip at the loading end is greater than that at the free end;the time-varying slip increases nonlinearly with time;the slip increases rapidly in the early stage and tends to be stable in the later stage;the laws of change of time-dependent slips between the two reinforcement materials and concrete are similar,but the slip between GFRP bar and concrete is much greater than that between ordinary rebar and concrete.