Abstract: The low elastic modulus of FRP bars and their non-yielding characteristics result in large deflections and wide cracks in concrete beams reinforced with FRP bars. Consequently, in many cases, serviceability requirements may play a major role in the design process. Based on analyses of calculation methods for the deflection of FRP concrete beam abroad, the experiment of 2 groups and 5 concrete beams under vertical loads at three-dividing point was conducted. According to the load-deflection curve and an assumed bilinear moment-curvature model determined by the crack moment and the ultimate moment of cross-sections, an analytical formula for predicting the deflection of FRP reinforced concrete beams was proposed, by which the calculated and the experimental results matches well.