In the flight process of a rudder wing structure in a hypersonic environment, a large temperature gradient is generated due to severe aerodynamic heating, leading to structural strength failure or ablation failure under the coupling effect of thermal stress aerodynamic force. Therefore, this paper proposes a method to study the ablation behavior of the hypersonic rudder wing structure. Based on the basic theories of hypersonic aerodynamics and structural mechanics, a fluid–solid–thermal coupling model of the rudder wing structure in a hypersonic environment is established. The temperature distribution and deformation of the rudder wing structure in the service state are obtained. In addition, the finite element analysis method based on automatic remeshing simulates the ablation of the rudder wing structure in a hypersonic environment. Under inflow conditions, the leading edge of the rudder has high temperatures and large deformation. The ablation simulation results are compared with the wind tunnel test results, and the results show that the proposed method can be applied to the study of service behavior in a hypersonic environment.