Abstract: A series of laboratory tests using the axial translation method, filter paper method and vapor equilibrium method on red clay including a unimodal (slurry) and a bimodal (compacted soil) pore-size distribution are performed to investigate the influences of the initial void ratio and pore structure on the soil-water characteristic curves (SWCCs) in the full suction range of 0~286.7 MPa as well as the hysteresis effect and volume variation during wetting-drying cycles. The test results show that whether the slurry or compacted soil, the influences of the initial void ratio on the SWCCs are mainly reflected in the lower suction range. The pore structure has significant influences on the SWCCs, and the SWCC of compacted soil and slurry are characterized by "double steps" and "single step". The air entry value and water holding capacity of slurry are greater compared to those of compacted soil with the same initial void ratio. The hysteresis effect of the compacted soil is obviously smaller than that of slurry, but the volume variation of slurry is larger during wetting-drying cycles.