Abstract: As a representative reactor type of the fourth-generation advanced nuclear energy systems, the high-temperature gas-cooled reactor (HTGR) has drawn extensive attention due to its inherent safety and high-temperature characteristics. The pebble-bed HTGR developed in China involves numerous randomly distributed fuel pebbles. The complex geometric structure poses technical challenges for core simulations. Current methods often employ approximate treatments such as spatial homogenization, leading to insufficient simulation accuracy and potential impacts on the correctness of safety parameters. This study, taking the high-temperature gas-cooled reactor pebble-bed module (HTR-PM) as an example, realized equilibrium core modeling based on a high-fidelity neutronics/thermal-hydraulics/pebble-flow coupling simulation framework. The framework included neutron transport simulation with explicit pebble-bed geometry, thermal-hydraulic simulation with coupled porous media-single pebble heat conduction model, and discrete element simulation of pebble flow, using OpenMC, OpenFOAM, and LAMMPS, respectively, achieving single-fuel-pebble-resolution calculations. To model equilibrium core of HTR-PM, a matrix-iterative calculation method was proposed to rapidly simulate the core refueling process so that different refueling schemes could be evaluated and the optimal solution could be identified. The method simplified the burnup depth distribution of fuel pebbles loaded into the core into a 90-dimensional vector and employs matrix multiplication to compute the evolution of this vector after each refueling cycle. Since the matrix used depends solely on the refueling scheme and remains invariant with respect to the vector, this approach enables efficient computation of the evolutionary trends over thousands of refueling cycles for a given scheme. Consequently, it allows for rapid evaluation of the convergence behavior across different refueling schemes. The results indicate that the refueling scheme with fixed discharge burnup limit exhibits an unacceptably slow convergence rate and requires prohibitive computational effort. In contrast, the approach employing a fixed fuel replacement proportion achieves convergence after approximately 15 refueling cycles, demonstrating its capability to support high-fidelity equilibrium core simulations for HTR-PM. A high-fidelity coupling simulation was performed for the HTR-PM refueling process with the fixed fuel replacement proportion scheme, reaching ideal equilibrium core condition with convergent results for effective multiplication factor, power distribution, temperature field, burnup distribution, and nuclide concentration. The single-fuel-pebble-resolution results demonstrate that the equilibrium core parameters, including power distribution, temperature distribution, and burnup depth distribution, align well with physical expectations. Moreover, key safety parameters such as the maximum single-pebble power and the peak fuel temperature remain within design limits.