In the structure reinforcement design of underground masonry drainage arch culvert, to simplify the calculation, the original arch culvert structure and the surrounding soil are equivalent to the reaction spring. In order to determine the correctness of the arch culvert reaction spring stiffness parameters and explore the factors that affect the stiffness of the arch culvert reaction spring, the finite element method was used based on the test section of Hongqiqu project. The material strength of masonry arch culvert, and the bearing capacity and Poisson's ratio of foundation soil layer were analyzed. The influence of moisture content of outer soil layer and plain fill soil layer and Poisson's ratio on the reaction spring stiffness of masonry arch culvert was considered. The results show that, the reaction spring coefficient of side wall increases with the increase of mortar strength of original mortar rubble side wall. The reaction spring coefficient of arch ring increases with the increase of the strength of the original brick arch ring mortar and brick block. The reaction spring coefficient of side wall and arch ring increases with the increase of foundation soil bearing capacity. The reaction spring coefficient of side wall increases with the increase of Poisson's ratio of foundation soil layer, outer soil layer and plain fill layer. The spring coefficient of arch ring reaction decreases with the increase of Poisson's ratio of foundation soil layer, outer soil layer and plain fill layer. The reaction spring coefficient of side wall and arch ring decreases with the increase of water content of outer soil layer and plain fill layer. The original masonry arch culvert and the surrounding soil are equivalent to the reaction spring boundary conditions calculated from the finite element method, then the whole structure reinforcement was calculated. The calculation results are compared with the monitoring data. The results show that the equivalent reaction spring stiffness of the arch culvert calculated by the finite element method is reliable.