Externally bonded prestressed carbon fiber reinforced polymer(CFRP)sheets for reinforced concrete(RC) beams strengthening is becoming an effectiveness strengthening method recently,especially to increase the service life under fatigue loading.Though there are some researches on the behavior of RC beams strengthened with prestressed CFRP sheets under static loading,however,researches on the improvement of fatigue performance are very limited. In this paper, the flexural fatigue behavior of RC beams strengthened with prestressed CFRP sheets is investigated with 7 specimens,in which the influences of strengthening amount of prestressed CFRP sheets,ratio of reinforcement,variable -amplitude fatigue loading and damage before strengthening are taken into consideration.Experimental results show that the stress amplitude of the tensioned bar is decreased remarkably and the fatigue life is then obviously increased as compared to normal strengthening method.