In order to study the bonding behavior and final failure modes of glass fiber reinforced polymer(GFRP) bars embedded in concrete, a total of nine pairs of specimens are tested under uni-directional pull-out loading. The variables involved in the experiments are the anchorage length of GFRP bars, the GFRP bar diameter and the concrete strength. The experimental results demonstrate that: (1) The bonding strength between GFRP bars and concrete increases significantly with the increase of bonding length and concrete strength. (2) For specimens fabricated with the 12 mm in diameter, the ultimate tensile capacities increases from 24. 4 kN to 71. 5 kN with the GFRP bar anchorage length varies from 30 mm to 120 mm. (3) For specimens with the same geometrical configuration (S-4, S-8 and S-9), the ultimate tensile capacity increases from 55. 4 kN to 71. 5 kN with the concrete strength varies from C30 to C50. (4)The failure modes of the specimens vary from GFRP bar rupture to GFRP bar pull-out failure or concrete splitting with the increase of bar diameter and bonding length, respectively. (5) The observed load-slip curves of the specimens can be divided into 4 phases, i. e. micro-slip stage, slip stage, declining stage and residual stage. The research results can provide reference for the application of GFRP bars in concrete structure.