Abstract: Gas permeability of compacted bentonite can provide the key parameters for the stability analysis and long-term safety evaluation of the buffer material, and then provide the basis for the construction of deep geological repository for high level radioactive waste.The experiments were carried out to study gas permeability of compacted bentonite with different dry density under different loading pressure and confining pressure.The results show that the gas permeability coefficient is negative quadratic function correlation with the dry density.The gas permeability remarkably decreases with the dry density.When the dry density changes from 1.4 g/cm³ to 1.8 g/cm³, the gas permeability coefficient gradually reduces from 10^-15 m² to 10^-17 m².Meanwhile, the gas permeability also corelate with loading pressure and confining pressure.It gradually reduces to a constant value with increase of confining pressure under the same rario of loading pressure and confining pressure.Measuring the gas permeability coefficient of compacted bentonite when loading pressure is more than 200 kPa, it is recommended that the ratio of pressure to confining pressure is 1∶3.