Abstract: Saturated-unsaturated state is a natural state of soils. Hence, unsaturated soil mechanics has wide applications in seepage analysis of earth and rockfill dam, contaminant transport, seepage and phase transform of frozen soil, and stability analysis of slope and embankment. As a fundamental relationship, the soil-water characteristic curve(SWCC)plays an essential role in the research of unsaturated soil mechanics. Python language is employed to develop the unsaturated seepage and stability analysis(USSA)software as well as the graphic user interface(GUI)for data processing and data fitting of SWCC curve. Based on a practical slope example, the whole analyzing process is described in details. It is from the data processing and data fitting of SWCC curve to unsaturated seepage analysis and stability analysis. The stability of dam under unsaturated seepage is conducted using the fitted parameters of SWCC model. The numerical results show that the stability evolutions of two dam slopes are quite different under the changing process of water level. When applying the shear strength reduction finite element method to the slope stability of unsaturated soil, the final FOS appears to be the lowest envelope of those FOS curves of all slopes.