This paper presents an experimental study of the flexural defections of concrete beam reinforced with basalt FRP bars. Six concrete beams with different BFRP reinforcement ratio and one comparative beam reinforced with steel rebar are tested in laboratory. Numerical simulations using sectional analysis method and spatial FEM are performed. The experimental results can fit well with numerical simulation results. Analysis and experimental results in the literature collected indicate that the ACI-440.1R-06 equations underestimate the deflection of FRP-RC beams. Based on the experimental and numerical simulation results, a modified equation of the flexural rigidity is proposed to calculate the deflection of the FRP-RC beams. The proposed equation can fit better with the experimental results than the ACI-440.1R-06 equations.