In this study, a finite element model for the simulation of the mechanical behavior of FRP-concrete beams is presented. The computational model includes the combination of two user subroutine UMATs for concrete and FRP material, and surface – based cohesive behavior to represent the interfacial bonding between concrete and FRP. The main investigations analyze FRP-concrete composite beams with three different types of surface – treatment, including non-treatment surface, sand-bonded surface and gravel-bonded surface. The numerical results show a very good agreement in compare with the experimental results.