Based on the pull-out test of center bonded specimen between the HRB400E crescent steel bar (HRB400E-CSB) and recycled aggregate concrete (RAC), the effect of the replacement rate of recycled fine aggregate and the dimeter of the steel bar on the bond-slip performance between the HRB400E-CSB and RAC was studied under the condition that the replacement rate of recycled coarse aggregate was 100%. Results show that the ultimate bond stress and initial bond stiffness between HRB400E-CSB and RAC decrease with the increase of the replacement rate of recycled fine aggregate and the steel bar diameterand the calculation formular of the ultimate bond stress of HRB400E-CSB and RAC is given by the least square method.