Abstract: In this paper, interaction between GMZ Na-bentonite sampled from Xinghe county, Inner Mongolia and Beishan BS05 groundwater of Gansu Province was carried out in glove box under ambient temperature and low-oxygen whose concentration was less than 0.005‰ condition for about 1 year. The variation characteristics of pH and Eh of bentonite groundwater system with time were investigated. The concentrations of key cations in liquid were obtained. Chemical composition, exchangeable cations and chemical composition of bentonite after reaction were determined. At mean time, the structure of bentonite was analysised using Raman spectrometer. The results show that bentonite-groundwater system can maintain a relatively stable state in experimental condition and time range.