The soil water characteristic curve of 56 soil samples from different landform types and different kinds of soil texture in Nanxiaohegou basin was tested, and the one-parameter model of soil water characteristic curve was established based on experimental data of 56 soil samples in Nanxiaohegou basin , Gansu Province, China. The model was proved by the measured data. The results indicate that one-parameter model has high accuracy and can be used to describe the soil water characteristic curve. The unique parameter of the model can be used as the variable coefficient to describe the spatial variability of soil hydraulic properties. It is useful in describing the spatial distribution of soil water characteristic curve in basin scale.