This paper attempts to reveal the flexural behaviors of concrete slab reinforced with GFRP bars. Through flexural test, the deformation process and failure mode of concrete slabs reinforced with GFRP bars and steel bars are examined, respectively. The deflection, cracking load, ultimate load and concrete strain are compared between two kinds of concrete slabs. From the test results, it is clarified that the moment-deflection curve of GFRP reinforced concrete slab can be divided into two stages. Before concrete cracks the behaviors of two kinds of concrete slabs are almost the same. However, the deflection of concrete slabs reinforced with GFRP bars increases much faster after cracking and the stress-strain diagram is linear up to rupture with no discernible yield point. The ultimate load of concrete slabs reinforced with GFRP bars is 1.2 times of that of concrete slabs reinforced with steel bars. Based on the test results, finite element analysis is performed in order to study the influence of reinforcement ratio. Parameter analysis shows that the flexural rigidity of GFRP reinforced concrete slabs increases with the reinforcement ratio after cracking.