Until now, there has been limited research on the bond behavior of ribbed Fiber-Reinforced Poly-mer (FRP) bars. In the paper, bond test data of the spirally-glued FRP bar and mechanically-grooved FRP bar were collected to investigate the test parameters on the bond behavior. Results show the macroscopic failure mode for the two types of ribbed FRP bars is pullout failure. More specifically, spirally-glued FRP bars mainly exhibit shearing off of FRP bar ribs, while slight dam-age occurs in concrete. Most grooved FRP bars show shearing off of concrete ribs, and bond strength increases with the increase of concrete strength for both FRP bars. Spirally-glued FRP bars show higher bond strength by increasing concrete cover which contributes to better confinement to FRP bars, but this seems to have no effect on grooved FRP bars. Bond strength of spirally-glued FRP bars can be improved by increasing relative rib height hrd and FRP bar rib width ratio FR. While grooved FRP bars are almost unaffected by hrd, and are mainly influenced by concrete rib width ratio CR, having higher bond strength by increasing CR. The calculated results by the pro-posed equations are in good agreement with the test results with greater accuracy than the design codes. This is because the effect of rib forming process and geometrical features of ribbed FRP bars on bond strength is accurately accounted in the proposed equations.