To reduce the permeability of clay liner, and make it has anti-cracking performance. Permeability and anti-cracking properties were studied on different Silica fume added to clay liner. 0、10%、15%、20%、15%、30% of the clay is replaced by silica fume at optimum water contents. It is shown by test results that permeability and width of crack is increased with increasing content of silica fume between 0 and10%, permeability and width of crack is reduced with increasing content of silica fume between 10 % and 20%, permeability and width of crack is increased with increasing content of ash between 20 %and30%, permeability and width of crack is the minimum is found for the 20% silica fume added to clay liner. According to the experimental data and experimental results, the best proportion is 20%，permeability is directly proportional to width of crack.