To reveal the influence of calcium lignosulfonate on hydrological properties of Lanzhou loess, based on different content of calcium lignosulfonate and age, the water repellency, permeability and water stability are analyzed through tests of water droplet infiltration, permeability and disintegration. And the mechanism of loess improved by calcium lignosulfonate is discussed by tests of X-ray diffraction and scanning electron microscope. The results show that: loess improved by calcium lignosulfonate can improve the water repellency and water stability, which of low content has limited improvement, but which of high content has large improvement. The effect of reducing permeability is limited. The loess improved by calcium lignosulfonate can show age effect in the hydrological properties. At 28 days, there is a generalized peak value in the hydraulic property parameters of loess improved by calcium lignosulfonate with the content, but the relationship between peak value and content is different. The hydrological properties and mechanical properties of loess improved by calcium lignosulfonate maintain a certain positive correlation. Loess improved by calcium lignosulfonate does not produce new mineral components. The thickness of electric double layer becomes thinner, and cementation products wrap particles, bind particles and fill pores, what improve the hydraulic properties.