Abstract: In order to solve the support problem of extremely thick coal seam in large section roadway in Yongdingzhuang Coal Mine, the loose circle thickness of the roadway is measured by borehole camera technology, support scheme for the roadway and its on-site application are designed based on loose circle theory, and numerical simulation is used to reproduce the roadway's excavation, deformation, support and stability process. The calculation results show that the combined arch effect of the support program in numerical simulation is consistent with the expected results; the support effects are fairly good.