Recently, Fiber sheets have been used for strengthening the deteriorated RC slabs because of its resistant capacity of corrosion and easy repairing works. This paper tested RC slabs reinforced with glass fiber sheets and carbon fiber sheets to study its flexural behavior. The strengthen effect and the static behavior was examined. Test parameters are the strengthening material, the number of sheet layer and strengthening direction. The behavior of strengthened RC slabs are represented by crack, load-deflection curves, maximum load and ductility. And the parametric study based on the nonlinear FEM analysis is performed and its results are discussed.