Abstract: Water seepage and freeze-thaw deterioration of concrete dams in cold areas is the main reason for safety risks such as dam failure, breach and even dam break.The hydrophobic treatment of dam concrete is an urgent problem to be solved in engineering practice.A novel hydrophobic agent named YA(Zeolite powder after surface modification)was applied to the hydrophobic treatment of concrete in this paper.The water-binder ratio of concrete specimens was 0.5,and four kinds of YA content(0,2%,3%,and 4%)were designed to study the mechanical properties and freeze-thaw resistance.Meanwhile, the water absorption test and mercury intrusion method(MIP)were carried out to obtain the pore structure, and the pore size distribution was used to analyze the improving mechanism of the concrete induced by YA.The results showed that the hydrophobic agent YA improved the internal pore network of concrete by increasing the number of transition pores and decreasing the number of macro pores, and further inhibited the intrusion of water and solution.The mechanical properties, water absorption and freeze-thaw resistance of the concrete were improved significantly.