Radioactive wastes arising from a wide range of human activities are in many different physical and chemical forms, contaminated with varying radioactivity. Their common feature is the potential hazard associated with their radioactivity, and their disposal is of vital importance to the protection of human environment. The geological disposal is commonly regarded in the world as the most reasonable and effective way to the safe disposal of high-level radioactive wastes. The conceptual model of geological disposal in China is based on a multi-barrier system that combines an isolated geological environment with an engineered barrier system. The buffer is one of the main engineered barriers for HLW repository. The buffer material is expected to maintain its low water permeability, self-sealing property, radio nuclides adsorption and retardation property, thermal conductivity, chemical buffering property, overpack supporting property, and stress buffering property over a long period of time. Benotite is selected as the main content of the buffer material that can satisfy the above requirements. GMZ deposit is selected as the candidate supplier for Chinese buffer materials of high level radioactive waste repository. This paper presents geological features of GMZ deposit and basic property of GMZ Na bentonite. GMZ bentonite deposit is a superlarge scale deposit with a high content of montmorillonite (about 75%), and GMZ-1, which is Na-bentonite produced from GMZ deposit, is selected as a reference material for Chinese buffer material study.