Abstract: The bond-slip constitutive model is often used to describe the interface behavior of glass fiber reinforced polymer (GFRP) bars to engineered cementitious composite (ECC). Although significant efforts have been made on the bond-slip relation of GFRP bar to normal concrete, few studies have focused on GFRP bar/ECC interface, particularly in the exposure of some special environments, including alkaline-saline conditions or freeze-thaw cycling. Therefore, this study aims to derive the bond-slip model for GFRP bar to ECC material in these environments through experimental and analytical study. 66 GFRP bar/concrete specimens were designed to gain an understanding of critical factors, including surface treatment of GFRP bars, matrix types and concrete strength, under three different conditions (i.e., ambient environment, alkaline-saline solution, and freeze-thaw cycles), on how to affect the failure modes, bond mechanism and bond-slip curves. The test results show that the pullout failures with cracks mainly occur on ribbed GFRP bar/ECC specimens. After freeze-thaw cycles, ribbed GFRP bar/normal concrete specimens change from splitting failure to pullout failure with cracks; The slope of bond-slip curves decreases. The residual branch curves of the specimens destroyed by pullout failure or pullout failure with crack attenuate in wave mode, and the difference of slips between the peak residual stresses is about a rib spacing of GFRP bar. And the difference of slips between the peak residual stresses is about a rib spacing of GFRP bar. In addition, the bond-slip curves were fitted with the existing bond-slip models. According to the fitting results and the actual bond-slip characteristics of GFRP bar/ECC interface under three different environments, a bond-slip model containing parameters A, B and α was proposed, and the fitting correlation coefficient R² was above 0.9, and the values of parameters A, B and α were concentrated in the range of −0.6-0.2, −0.1-0.1 and −0.6-−0.3, respectively. In addition, the accuracy and effectiveness of the proposed model were further verified using previous data from the literature.