A physical model derived from Darcy's Law and the continuity equation and abudget model based on water balance are used to simulate respectively the daily changesin soil water from the jointing to maturing phases for winter wheat grown in Jingyang,Shanxi in 1987 and 1988 and Tianshui, Gansu in 1986 located in the semi-arid zone.Both the models achieve good results as compared with measured values. The physicalmodel has higher accuracy than the budget model for predicting the water content in theupper soil layer. The latter model is more sensitive to the distribution of root,but the evapotranspiration predicted is on the high side and the percolation predicted on the lowside.