Abstarct: Abstract: Tunnels are one of the types of underground structures that play an important role in transportation, water transfer, communication lines and energy. Determining the appropriate curvature for the walls, roof and floor of horseshoe and dome shaped tunnels according to the direction and ratio of the amount of stresses in order to control tangential stresses is of great importance because choosing the optimal curvature reduces the amount of destabilizing factors on the tunnel lining and It is possible to reduce the volume and, as a result, the cost of the consumables of the support system in the tunnel section, and as a result, the construction cost and duration of the tunnel construction can be significantly reduced. In this research, two-dimensional finite difference modeling was used with the help of FLAC software to determine the optimal tunnel section (in terms of shape change, stress concentration, as well as volume reduction and as a result, the cost of consumables in the maintenance system). For this purpose, the tunnel with geometric sections with different radius of curvature for the walls, crown and floor has been examined for different ratios of horizontal to vertical stress, which includes different types of tunnels, including tunnels with circular, square, rectangular, and elliptical sections. And it is a horseshoe. The results of the research show that the cross-section of a horseshoe with a highly curved wall (the radius of curvature of the tunnel floor is 1.7 meters, the radius of curvature of the tunnel walls is 4 meters, and the radius of curvature of the tunnel crown is equal to 5.2 meters) in total in terms of the values of stress concentration coefficient and induced stresses From the tunnel excavation and also the values of the tunnel deformation, it is considered the optimal section compared to the other examined sections. In terms of the maximum tangential stress values of the tunnel, for different values of the horizontal to vertical stress ratio, in the general state of the horseshoe section with a high curvature wall, it has the lowest values of the maximum tangential stress among the examined sections, so in general, this section can be considered as the section suitable among the sections reviewed, suggested.