Abstract: The time effects have a significant influence on the deformation characteristics of the overconsolidated unsaturated soils. Establishing an elastic-viscoplastic constitutive model for the overconsolidated unsaturated soils considering the time effects is of great significance for accurately analyzing the time-dependent deformation characteristics. Based on the unified hardening model for the overconsolidated soils, an elasto-viscoplastic constitutive model for the overconsolidated unsaturated soils is established, considering the degree of consolidation, matric suction and time effects. Firstly, according to the elasto-plastic deformation characteristics of the overconsolidated soils, the one-dimensional elasto-viscoplastic constitutive model for the overconsolidated soils under continuous loading condition is modified by introducing the unified hardening parameters. Secondly, by using the Barcelona model yield surface of the unsaturated soils and based on the over-stress theory, an elasto-viscoplastic model considering the time effects and the influences of suction is established. Compared with the Barcelona model, an additional viscosity coefficient related to the time effects is introduced. The comparative results of model verification and experimental data show that the proposed model can reasonably predict the time-dependent deformation characteristics of the overconsolidated unsaturated soils.