A model based on the physical process of water absorption by plant roots has been suggested in this paper. Data obtained from the comparison between modeling results and experimental results showed that this model is quite satisfactory for prediction of soil moisture regime. Quantitative description of water potentials in soil, plant and atmospliere. In describing the interlinked process of water transport was made in the modelling water movement process, and the characteristics for process of energy consumption and transformation in the water movement process was also investigated simultaneously. It was also showed from the results obtained that the relationship between water absorption was close related to the effective root density. Therefore, it is of most importance to promote and strengthen the development of plant roots.