Compacted bentonite is an ideal buffer/backfill material for high-level waste repositories, and its hydration swelling pressure is critical to the structural stability of the repository. The swelling pressure generated during its hydration is a result of the combined effect of the montmorillonite swelling and the multi-scale structural adjustment. In this paper, the multi-scale structural characteristics of compacted bentonite are described, and the research advances of the cross-scale swelling pressure transfer mechanism and theoretical model are systematically summarized. It shows that the hydration cleavage of quasicrystals has an effect on their surface electric potential, increasing the negativity and exacerbating the swelling capacity. The hydration process causes the number of pores to increase and the volume to decrease, resulting in the unloading effect of quasicrystals and aggregates around the pores, which leads to the attenuation of the swelling pressure in the crossscale transmission. However, existing studies have not yet quantitatively evaluate the cross-scale transfer mechanism of swelling pressure, and the influence of multi-physical fields on the transfer mechanism is not clear. Corresponding cross-scale swelling pressure correlation models have been established based on the structural characteristics of different scales, but they have not yet quantitatively evaluated the effect of hydration swelling pressure on the physical mechanics of their pore structures. Based on this, revealing the physico-mechanical principles of pore structure evolution in the hydration process, exploring the influence of multi-physical fields on the swelling pressure transfer mechanism, and constructing the theoretical models for cross-scale swelling pressure transfer are the focuses of future research. And the structural state set theory provides a new idea for the establishment of a unified system of compacted bentonite swelling pressure cross-scale transfer model by dividing the microstructure elements.