Abstract: Based on the Jingshengwu tunnel of the Quzhou-Jiujiang railway, the construction steps of mining meth? od with arching and backfilling are introduced, an calculation formula for the rock load sharing proportion of the arching structure and primary support arch structure is deduced by elastic theory, a mechanical model of surrounding rocks at sidewall is established by ultimate equilibrium theory, and a formula for calculating additional surrounding rock pressure on the sidewall of primary support is derived, the internal force and safety factors of arching structure and primary support structure are calculated by establishing a load-structure model, and the safety of arching structure and primary support structure is evaluated. The results show that: rock load sharing proportion of primary support is related to elastic modulus and thickness of arching structure and primary support structure, the rock load sharing coefficient of primary support of Jingshengwu tunnel is about 30%; the vertical pressure at arch spring of arching structure causes the rocks above sidewall slide along the fracture surface and horizontal additional surrounding rock pressure is produced at the upper sidewall of primary support; the arching structure and primary sup? port structure of Jingshengwu tunnel are in safe state, the safety of primary support slightly decreases with the increase of rock load sharing factor.