Abstract: The geological disposal of high-level radioactive wastes can realize long-term containment and isolation to radioantive wastes by multi-barrier systems constructed of natural barriers (surrounding rock) and engineering barriers. The buffer materials basically composed of bentonite rich montinorillonie were built up an important engineering barrier, which ought to be of good thermal conductivity, low permeability, stable chemical and favourable mechanical properties, a strong ability to absorb nuclides and so on. They must ensure a certain saturated density in the disposal environment for a long time. The sizes of disposal holes, blocks and containers, the densities and moisture contents of buffer materials significantly influenced on saturated densities of buffer materials. Based on properties of Gaomiaozi bentonite of Inner Mongolia, combined with the conceptual design of high-level radioactive-waste geological disposal and design requirements of buffer materials, parameter influencing factors of saturated densities for buffer materials were analyzed, which could provide reference to the design of buffer materials for geological disposal of high-level radioactive wastes in China.