The structural performance of concrete structures reinforced using glass-fiber-reinforced-polymer (GFRP) rebars is sometime compromised by debonding failure. For better analyzing the GFRP bar-concrete bond behavior, this study presents two damage-based approaches for assessing the bond damage evolution. One is the secant modulus-based model and other is exponential damage model. Using the exponential damage approach, a simplified analytical model based on only one curve fitting parameter was developed to predict the bond stress-slip relationship. Then, a 3D finite element (FE) model was developed and both proposed damage-based approaches were implemented, to simulate the GFRP bond behavior. The FE model considers the nonlinear behavior of the concrete and the GFRP bar-concrete interface. The analytical and numerical predictions of the GFRP bar-concrete bond behavior are validated by comparing with the relevant results of an experimental program focused on quasi-static pullout tests. At the end, a parametric study was carried out to numerically assess the influence of some critical parameters on the bond behavior.