<p>Bentonite pellets are utilized to fill gaps between the buffer layer, comprised of compacted bentonite blocks, and the surrounding rock in a deep geological repository (DGR) for disposing nuclear waste. Thermal contact resistance (TCR) arises at the interface due to the imperfect contact between the compacted bentonite blocks and the bentonite pellets. TCR is one of the parameters influencing the thermal performance of DGRs, therefore, understanding the TCR between bentonite blocks and pellets is essential for accurately assessing the thermal performance of DGRs. To this end, a testing system based on the steady-state method has been developed and implemented to measure the TCR. Utilizing this system, the TCR at the interface between bentonite block and pellets was evaluated under various conditions: temperature, dry density, water content and particle size distribution. The results indicate that the TCR of the interface between bentonite block and bentonite pellets is on the order of 10^–2&#xa0;°C·m²/W. TCR increases with the difference between the thermodynamic properties of bentonite block and pellets increasing. Particle size distribution significantly affects the TCR, with mixtures containing only coarse particles exhibiting the highest TCR. Incorporating fine particles into these coarse pellet mixtures effectively reduces the TCR. As the mass fraction of fine particles increases, TCR initially decreases and then increases. TCR decreases as temperature rises, with a more pronounced decrease observed between 50&#xa0;°C and 70&#xa0;°C, while the decrease is less significant from 70&#xa0;°C to 130&#xa0;°C. Furthermore, multi-parameter sensitivity analysis revealed that the dry density of bentonite block has the most significant influence on the TCR, whereas heating temperature has the least influence.</p>