Constitutive models for rock under cyclic loading and unloading, which are rarely reported in literatures, are critical to predict the long-term stability of CAES caverns. A constitutive model for rock subjected to cyclic loading and unloading is proposed. The model for rock softening and damage, which is based on Weibull random distribution, is expanded. The fatigue constitutive model with internal variables is employed to describe the variations of initial modulus and unloading modulus during every cycle. Then, a constitutive model for rock under cyclic loading and unloading is obtained. The results from proposed constitutive model is subsequently compared with the existing test results. The physical meaning of this model is explicit. The parameters involved in the model are less and can be easily fitted. The proposed model can represent the relationship of the stress and strain of every cycle and shows a good agreement with the results of laboratory tests. The successful establishment of the proposed model can provide a new idea to the researches on constitutive models for rocks under cyclic loading and unloading.