The mechanical behaviors of the combined system consisting of shield tunnel segment and reinforcement structure during and after fire scenarios are analyzed by the means of experiment. The experiments are conducted under 50 ℃, 100 ℃, 200 ℃, 250 ℃ and 300 ℃ to test the failure modes of the interface, the relationship between load and displacement and the temperature damage load. The experimental results indicate that: 1) The failure of the interface between the C50 concrete cube and the composite structure can be divided into 2 types. Failure mode 1 occurs under relatively low temperature (20 ℃, 50 ℃, 100 ℃ and 200 ℃) and mode 2 occurs under relatively high temperature (250 ℃ and 300 ℃). 2) The tensile stiffness of the interface reduces with the temperature increase; the major factors affecting the tensile properties of the interface after exposure to relatively low temperature (20 ℃, 50 ℃, 100 ℃ and 200 ℃) and relatively high temperature (250 ℃ and 300 ℃) is the tensile strength of the concrete and the bond property between the binder and the concrete respectively.