Abstract: The concrete linings of underground river-crossing tunnels bear the cyclic load of vehicles during its service, which leads to different degrees of mechanical damage in concrete linings, thus weakens the impermeability of concrete lining.Therefore, the triaxial cyclic loading and unloading test was carried out for high performance concrete.The evolution of the deformation and mechanical properties, mechanical damage characteristics and impermeability of high performance concrete in the whole process of triaxial cyclic loading and unloading were studied.The results show that:(1) The mechanical damages of concrete caused by cyclic loading and unloading increase with the increase of cycles, and it shows a good exponential evolution relationship with the plastic strain.(2) The evolution of concrete permeability under cyclic loading and unloading can be divided into three stages: stable period, rapid growth period and slow change period.Among them, the confining pressure level has an obvious influence on the first stage and the third stage.(3) The three-stage evolution law between permeability and mechanical damage of concrete can be well described by Logistic empirical model, and both of them decrease with the augmenting of confining pressure.The research results are helpful to understanding the evolution mechanism of impermeability and mechanical damage of high performance concrete in the whole process of triaxial cyclic loading and unloading, and provide a reference for determining the mechanical damage and impermeability of concrete structures under different stress levels.