Abstract: In order to study the influence factors of bonding properties of glass fiber reinforced polymer (GFRP) composite bars and engineered cementitious composites (ECC), pull-out tests on forty-two GFRP/ECC testing specimens were designed and carried out. The influences of the surface form of GFRP composite bar, the diameter of GFRP composite bar, the strength of ECC matrix, and the thickness of the concrete cover on the bonding properties of the interface between GFRP composite bars and ECC were analyzed. The results show that there are mainly three failure modes, namely pull-out failure, peeling off of resin, and splitting failure. The bonding strength at the interface of GFRP composite bars with ribbed surface form is about 66% higher than those plain round GFRP composite bars. When the thickness of ECC concrete cover increases from 1.5D to 4D, the bonding strength of GFRP/ECC increases by about 58% (D is diameter of GFRP composite bars). When the diameter of CFRP composite varies between 12~18 mm, the bonding strength of GFRP/ECC decreases with the increase of CFRP composite bar diameter. When the strength of ECC increases from 33.7 MPa to 73.3 MPa, the bonding strength of GFRP/ECC increases about 3 times. Increasing the complexity of the surface form of GFRP composite bars, or to some extent increasing the thickness of ECC matrix protective layer and the strength of ECC can help to improve the bonding strength between GFRP composite bars and ECC.