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Based on the variable amplitude loading tests of nine RC members, the possibility of giving the performance division standard for the damage process under different variable amplitudes according to the stiffness reduction index was studied. The influence of the duration of earthquake, peak displacement, longitudinal ratio and stirrup ratio on the damage of RC members were also discussed. It was found that the stiffness reduction index provided a unified standard of performance division for RC members under different variable amplitudes, and five performance levels (no damage, mild damage, moderate damage, severe damage and destruction) according to the capacity reduction index are proposed. The standard is verified by nine flexural failure specimens of rectangular section in the PEER database; The stiffness reduction index is in accordance with the peak deformation index in defining the light damage of RC members while the stiffness reduction index is in good agreement with the Park-Ang damage index in defining the moderate and severe damage of RC members. Based on the case study, the relationship between the stiffness reduction index and the stirrup ratio, and that between the effective duration and the ductility coefficient are discussed. [ABSTRACT FROM AUTHOR]