Abstract: The Pebble-bed High Temperature Gas-cooled Reactor utilizes unique coated fuel particle design, which is embedded within a graphite matrix and shaped into spherical element with graphite shell and coolant outside. The inherent double heterogeneity of spherical fuel element requires special simulation strategy in both modeling and resonance calculation, where graphite cross sections play significant role considering the large quantity and neutron moderation effect of graphite in pebble-bed HTR. In this study, neutronic calculations with both ENDF/B Ⅶ.0 and ENDF/B Ⅶ.1 nuclear data libraries were performed for various fuel models using SCALE/KENO-Ⅵ and Serpent-2 codes. The results show that using ENDF/B Ⅶ.0 library leads to significant under prediction of multiplication factor when compared with results using ENDF/B Ⅶ.1 library and the deviation varies with model scale, about 200 pcm for coated particle model, about 700 pcm for fuel element and about 1 600 pcm for core unit. The results of single spherical fuel element with SCALE DOUBLEHET treatment were compared with those using explicit lattice model and it is found that the DOUBLEHET treatment produces consistent numerical results while saving about 85% computing time.