Experimental research was conducted to investigate the characteristics of various CFRI strengthening methods and effective depth of beam. A total of 12 specimens were tested in foul point bending after strengthening them with externally bonded CFRP plates. The CFRP plates were bonded without prestress or with prestress levels of CFRP plate strain 0.6%. The non-prestressed specimen without anchor plate failed by separation of the plate from the beam due to premature debonding while the non-prestressed specimen with anchor plate failed by CFRP fracture and showed the significant increase of ductility capacity. In addition, the prestressed specimens failed by CFRP plate rupture. The maximum load and ductility capacity were most significantly increased. And it was founded the increasing ratio of ultimate load as to strengthening methods tends to decrease in case of the increase of effective depth of beam.