Abstract: A series of water retention tests and mercury intrusion porosimetry tests on a clay are performed to investigate the influence of different specimen preparations on water retention behaviour and its pore-size distribution as well as the influence of different isotropic stresses on water retention behaviour. The experimental results show that pre-consolidated specimens exhibit a unimodal pore-size distribution, and unsaturated compacted specimens usually have a double-porosity microstructure, while its microstructure can change due to saturation at the applied pressures of 20 kPa. Under the same initial void ratio and isotropic stress, the pore sizes of pre-consolidated specimens exhibit a uniform distribution, so they have higher air-entry value than the compacted specimens. Under the same initial void ratio of pre-consolidated specimens, the air-entry value increases with the increasing isotropic stress. Finally, based on the results of the mercury intrusion porosimetry tests, a method for predicting the water retention curve of pre-consolidated and compacted specimens during drying is proposed, and the predicted results are compared with the measured values.