Abstract: In this research, pull-out test was used to study the bond between GFRP ribbed rebar and concrete, aiming to determine the optimal surface configuration of GFRP ribbed rebar, and to build the bond-slip constitutive model of GFRP ribbed rebar to concrete. The testing variables includes the rebar diameter, rib spacing and rib height. The test results show that the bond strength of GFRP ribbed rebar is improved obviously, which decrease with the increase of the rebar diameter. The failure mode is the shear of the concrete between the ribs of the rebar, and the slight damage of the rib surface. The bond behavior of these rebars varied with the rib geometries, such as the rebar rib spacing and the rib height. Theoretical analysis of the test results indicate that the bond strength depended primarily on mechanical interaction between the ribs of the rebar and the surrounding concrete. The effect of rebar diameter on bond behavior can be attributed to the shear lag of GFRP ribbed rebar. And the variation in bond behavior of GFRP ribbed rebar with different rib parameters can be ascribed to the wedge effect. Design recommendations are drawn from the results that the optimal rib spacing is of the rebar’s diameter, and the optimal rib height is 6% of the diameter. The newly built bond-slip constitutive model fits the whole loading process of GFRP ribbed rebar well.