Permeability is an important property of soil. For the project such as the anti-pollution of the landfill, the seepage control of the dam and the leakage control of the foundation pit, the ultimate aim is to improve the impermeability of soil by various methods. Therefore, the clayey soil samples with different clay content were prepared and used for the permeability and related tests. The influence of clay content on the permeability can be analyzed by above tests. The results show that with the increase of clay content, the plasticity index of clayey soil increases linearly, while the permeability coefficient decreases nonlinearly which can be fitted by exponential function. According to the grain graduation curves, the samples with high clay content have small non-uniformity coefficient. It implies that the soil accumulation mode dominated by small particles, which makes pore diameter small and easy to appear disconnected pores. So the permeability coefficient of soil decreases. The results can be used for engineering practice.