The calculation formulas for concrete and steel utilization rate of reinforcing layer have been deduced, in view of the underutilization of reinforcing layer material by composite main arch circle method. The calculation formulas is defined as load bearing capacity of reinforcing layer divided by the ultimate bearing capacity of reinforcing layer, combined with initial strain of main arch ring before reinforcement and reinforcing layer section edge strain, take compression zone partial of reinforcing layer subjected to tension and compression as example. The calculation formulas for concrete utilization rate of reinforcing layer is divided into 2 types according to the height of compression zone and on the edge of compressive strain in the reinforcing layer, the calculation formulas for steel utilization rate of reinforcing layer is divided into 1 types according to tension strain of the steel. The results show that controlling the stress and strain of stone arch bridge before reinforcement can make full use of compression resistance on main arch ring, strength of materials and reduce the waste of materials relying on engineering example. The calculation formulas provide the theoretical basis for calculation and design of the similar reinforcement structure.