Abstract: The triaxial compression tests of concrete are carried out to study damage properties after different number of pore water cycles at a middle strain rate of 10-4 s-1. The relationships among mechanical properties including the peak stress, peak strain and elastic modulus with number of cycles are analyzed. And damage variable is defined according to the degeneration compressive tangent modulus. Thus, the curves of the stress levels-damage are obtained, and the damage properties of concrete are studied. The research results show that: ①after different pore water cycle, the peak stress and peak strain of concrete under the triaxial compression show an exponential increasing trend with numbers of cycles. The elastic modulus shows a decreasing trend of the power function with the cycles, and then becomes slow. ②damage growth rates under 10, 50, and 200 cycles are greater than that under 0 cycle as a whole, and it decreases with number of cycles. ③through the curves of stress levels-damage, the process of damage evolution can be divided into three parts: initial stage, development stage and instability stage. And according to the data of damage, the damage evolution equation is constructed by fitting. ④according to the three stages of damage development, the damage boundary points are defined. The relationships between the damage boundary points with length of stress level of damage and the different pore water cycles are analyzed. The stress level of the damage boundary points increases at first and then decreases with the pore water cycles.