Abstract: Fatigue strength is an important mechanical parameter for structural fatigue design. In this paper, 24 simple supported reinforced concrete (RC) beams strengthened with carbon fiber laminate (CFL) were divided into 5 groups and tested under cyclic bending loads. Based on the fatigue testing results, the S-N curves and the corresponding expressions of permissive fatigue lives and extreme fatigue lives are obtained, respectively. The ratio of permissive fatigue strength to static ultimate strength and the ratio of extreme fatigue strength to static ultimate strength are about 62% and 68%, respectively. Moreover, one new kind of curve is proposed for the fatigue lives of the beams, namely, the relationship curve between power rate of outer work, , and the fatigue lives, , is discussed. The values of the power rates corresponding to the fatigue strength of permissive fatigue lives and extreme fatigue lives are respectively established.