Abstract: Farmland pipe drainage is one of new engineering measures to improve saline-alkali soils. It is important to simulating farmland water and salt migration for the construction and management of a pipeline system on farmlands. In this study, the basic principle and parameters of the water management model DRAINMOD-S are comprehensively introduced on the bases of mathematically modeling flows and salt migration in saturated-unsaturated soils. The DRAINMOD-S model is used with the weather, soil and crop data collected from typical saline lands along coastlines to simulate the groundwater level for different arrangements of subsurface pipe drainage. Using the calibrated parameters, the salinity profile of 0-80 cm soil layer is simulated with the DRAINMOD-S model. The result shows that the DRAINMOD-S model performs well for hydrological simulation. Both groundwater level and salinity profile are in good agreement with observation. The DRAINMOD-S model is able to predict the groundwater depth in saline-alkali soils and the salt content in soils. The model is a useful tool for the design and management of a pipeline system on farmlands.