High-temperature gas-cooled reactors (HTGR), as a new type of nuclear reactor, have attracted significant attention due to their efficiency, safety, and sustainability. The study of dense particle flow, particularly the behavior of graphite spheres in the pebble-bed region, has become a key topic in nuclear engineering. The flow characteristics of graphite spheres under high pressure are not yet fully understood, especially the impact of dense particle flow mechanics on core thermal safety and operational performance. This paper use experiments to explore the flow characteristics of dense particle flow in silos under different gas flow rate and outlet sizes. In the future, developing more precise models and experimental methods for the particle flow behavior of graphite spheres in HTGRs will help enhance reactor design safety and reliability, providing theoretical support for the sustainable development of nuclear energy.