Abstract: To investigate the deformation characteristics and support optimization methods of roadways excavated in backfill under complex stress conditions, the stress distribution and roadway deformation failure characteristics of a copper mine in Serbia were surveyed. The stability of the backfill was evaluated based on a modified coal mine roof rating （mCMRR） system, and the support parameters for roadways excavated in the backfill were optimized by combining the analysis of roof bolt systems （ARBS） with numerical simulation. The results show that a high horizontal stress difference coefficient, fractured rock strata, and non-uniform stress transfer induced by intensive multi-level mining are the main causes of the complex stress regime in the mine, with roadway deformation characterized by roof crushing, apex failure, and shear staggering. The mCMRR value of the backfill in the bottom structure of the preliminary stope is 60.5, rated as "moderate" with a safety factor of 2.14. For the combined bolt-mesh-shotcrete support system in roadways excavated in the backfill, the existing bolt pattern can be optimized from 0.8 m × 1.0 m to 1.0 m × 1.2 m. Numerical simulation and industrial tests indicate that a support scheme consisting of roof bolts spaced at 1.0 m × 1.2 m, ϕ6 mm @ 100 mm × 100 mm steel mesh on the roof and sidewalls, and a 50 mm shotcrete layer, can effectively form a cooperative load-bearing structure of roadway and surrounding rock. The stress, displacement, and plastic zone distributions in the roof and sidewalls meet safety requirements, and the support cost is reduced by 8.3 %.