A B S T R A C T Fatigue performance of reinforced concrete (RC) components strengthened with fibre reinforced polymer (FRP) is largely improved. However, temperature changes of service environment have a great effect on the fatigue behaviour of RC components strengthened with FRP. Concerning about temperature variations in subtropical areas such as South China, this paper analyses the fatigue behaviour of RC beams strengthened with carbon fibre laminate (CFL) from experimental studies and theoretical analysis under four different temperatures (5 • C, 20 • C, 50 • C, 80 • C) and five different stress levels (0.60, 0.66, 0.72, 0.78, 0.84). The paper discusses temperature fatigue behaviour of RC beams strengthened with CFL under cyclic bending loads in different service environments, and proposes a calculation formula of fatigue lives of RC beams strengthened with CFL under environmental temperatures and external forces coupling. Experimental results show that the formula not only effectively predicts the fatigue lives of the RC beams strengthened with CFL under environmental temperatures and bending loads coupling but also estimates the fatigue limits. A 1 -A 3 = constants B = width of the beam section C = constant C 1 -C 5 = constants' coefficient to be determined by experiments H = height of the beam section m(T) = material performance index related to temperature N = load cycles, fatigue life of the strengthened beam P = external load P u = ultimate bearing capacity of strengthened RC beam under static load P max = maximum value of cyclic loads S = cyclic stresses S R = load level (stress level), S R = P max /P u S S = span length (distance between two supported points) T = temperature I N T R O D U C T I O NFatigue performance and durability of reinforced concrete (RC) beams strengthened with fibre reinforced polymer (FRP) are of great concern in the field of civil engineering. 1-8 For the fatigue behaviour research of RC beams strengthened with FRP, verification experimental studies of fatigue behaviours of carbon fibre reinforced polymer (CFRP) or RC components strengthened with CFRP have been carried out since last mid-nineties. [1][2][3][4][5] Research results indicated that CFRP sheets largely improved the fatigue lives of RC beams. The fatigue failure modes, fatigue failure mechanism, multi-layers bonding 708