Abstract: The soil-water characteristic curve (SWCC) is essential to describe the behavior of unsaturated soils. The capillary hysteresis is an important effect that should be accounted in the equations for SWCC. The existing SWCC models are mainly based on the equilibrium condition. However, there is ample theoretical and experimental evidence that the curve is not unique under dynamic conditions. The dynamic capillary pressure is larger than the static one in drainage and smaller in wetting. A thermodynamic theoretical basis for the SWCC under dynamic conditions is given. A dynamic capillary hysteresis model is developed based on the bounding surface plasticity. Provided that the main drying and wetting curves have been experimentally determined, the model is capable of predicting all the scanning curves. The model predictions are compared with the existing experiments found in the literatures, showing a good accordance with the test data for both the drying and wetting conditions. The results can then be used to explain some practical problems such as foundation settlement and slope stability.