Abstract: The joints of composite blocks of buffer materials as potential weak parts in the engineering barrier system of high-level radioactive waste (HLW) repository must be studied in depth. Therefore, the evolution of temperature and volumetric water content with time at different locations of Gaomiaozi (GMZ) composite bentonite samples before and after simulated water inflow is measured by using the developed experimental devices. According to the experimental results, the thermal conductivity and hydraulic conductivity of the joint location after healing of composite samples are obtained. The experimental results show that the change of the internal temperature of the composite bentonite samples is mainly affected by the temperature boundary, and the change of the internal water has small effects on it. In a short period of time, the loading of hydraulic boundary conditions only makes the volumetric water content of the soil near the hydraulic boundary increase significantly, but has small effects on other locations. Affected by the temperature boundary, the volumetric water content of the soil near the temperature boundary gradually decreases with time. The thermal conductivity and permeability of the joint location after healing can meet the requirements of the engineering barrier of the HLW repository.