SFG model has some advantages that it is more flexible in modeling different types of unsaturated soils than most other models in the literature. However, there are some shortages in SFG model. Firstly, it did not take account the influence of degree of saturation on the deformation of soil. Additionally, the SWCC that was adopted in the SFG model is relatively simple and cannot reflect the relationship between the current void ratio and the degree of saturation. This paper firstly presents the modified model based on the SFG model. The modified model adds the degree of saturation into the volumetric model for unsaturated soils. In addition, it adopts a SWCC that can reflect the influence of current void ratio. The new yield surfaces are proposed. These new yield surfaces are not only the function of suction and mean net stress, but also the function of the current degree of saturation and void ratio of soil. The modified SFG model can model more types of the behaviors of unsaturated soils and is more reasonable than SFG model.