Abstract: In the treatment of high-level radioactive waste(HLW),the use of bentonite-based buffer/backfill material as a geological disposal project barrier system is the most important encapsulation facilities to intercept radionuclide migration to water environment.It is optimized by an addition of certain content of quart sand to bentonite to improve the strength and heat conductivity without obvious lowering of permeability.A summary was made to illustrate the effects on the swelling parameters of compacted bentonite-sand mixture of some factors such as initial water content,dry density,bentonie content,pressure effort etc.,and to analysis the intrinsic permeability of bentonite-sand. Montmorillonite quality ratio is proposed in this paper.The dry density and the bentonite content are unitary,and they can be used to the mass analysis of swelling pressure.The research results provide valuable hint to the swelling of mixed backfill/buffer materials in China.