This paper quoted the Kirchhoff elastic thin plate theory to analyze the roof stress of frame culvert which traversed the railway subgrade. Taking a certain frame culvert of national highway traversing railway sub- grade in Nanchang as the research object, the expression of deflection was set in the form of a double trigono- metric series which were divided into general solution and particular solution to calculate the stress of frame culvert under the load of overlying soil and the load of train. The general constant of the general solution in the expression was determined based on the boundary conditions of the rectangular thin plate. Mathematical comput- ing software Wolfram Mathematica was used for theoretical calculation and the commercial software ABAQUS was adopted to set up the finite element model. The theoretical values obtained from the calculation were com- pared with those obtained by finite element analysis, and the comparison results were in good agreement. It is concluded that this theory can better meet the engineering needs of precision and it is proved that this method has good practical value in the analysis of the stress of frame culvert roof.