Abstract: Based on the isotropic compression tests on unsaturated soils and the Logistic function, a model for isotropic consolidation curve of soils is proposed. Firstly, the shortcomings of the single-logarithmic and double-logarithmic linear models commonly used in the volumetric behavior are analyzed. Then, with the Logistic function, the mathematical model between void ratio and pressure under isotropic compression conditions is established. The determination method for every parameter in the model and the analytical expression of the pre-consolidation pressure are given. Finally, the validity of the model is verified by comparison with the existing experimental data, and the influence of suction on each model parameter is analyzed.