Abstract: Taking compacted bentonite as the research object, the vertical swelling pressure of samples at different resting time was investigated by both experiment and theory. Firstly, bentonite powders with four different water contents were compacted to samples of two dry densities. Then, the compacted samples were rested for different periods (0, 1, 7, 15, 30 and 90 days). Afterwards, the samples were subjected to swelling pressure tests by using the swelling apparatus. Test results show that the maximum vertical swelling pressure of compacted bentonite decreases with the resting time. The swelling pressure decreases fast at the resting time of 0-7 days and then turns to be stable after 30 days resting. Based on test results, an empirical model considering aging effects of the swelling pressure of compacted bentonite is established. In the model, the swelling pressure decreases linearly with the logarithm of resting time. Discussion on the model parameters indicates that the initial swelling pressure increases linearly with initial suction whereas the decay index of swelling pressure decreases linearly with the increase of suction. Fitting results show that the established model can reflect well ageing effects of the swelling pressure of bentonite.