The temperature field in the rock surrounding a shallow-buried circular tunnel by considering the influence of the insulation layer is analytically investigated in this paper. The conformal mapping method is used to transform the heat conduction equation of the tunnel surrounding rock in Cartesian coordinates to one in the polar coordinate system, obtaining the expression of the heat conduction equation in polar coordinates. By applying boundary conditions and continuity conditions, the analytical solution for the steady-state temperature field in the rock surrounding a shallow-buried circular tunnel is obtained. Meanwhile, a finite element model is established to compare the analytical solution obtained in this study with the numerical solution. The consistency between the analytical solution and the numerical solution verifies the accuracy of the analytical solution proposed in this paper. The influences of tunnel radius, tunnel burial depth, insulation layer thickness, and thermal conductivity of the insulation layer on the steady-state temperature field in the rock surrounding the tunnel are analyzed. The research results are significant for the guidance of actual tunnel engineering projects.