Abstract: A cycle tensile test was carried out on the GFRP bars with diameters of 16 and 20 mm at the stress levels of 0.3, 0.5 and 0.6 and the stress ratios of 0.3 and 0.5. The residual stiffness evolution curves under different working conditions were obtained by characterizing the damage of GFRP bars with dynamic residual stiffness, and the validation and fitting results from experimental data were obtained according to the EEB and YLS models. The results indicated that, at the stress levels of 0.3 and 0.5, the YLS model could well characterize the fatigue damage characteristics of GFRP bars in most stages, whereas the EBB model was not in good agreement with the experimental results. According to the fitting curves obtained from experimental results, the curve fitting with piecewise exponential functions was found to better characterize the fatigue damage during the cycle tensile test.