In order to accurately assess the robustness of the complex bridge structure, a method of robustness assessment that takes structure degradation and accidental loads into consideration is proposed. Firstly, the degradation rates of member section properties and the increasing rate of live load are set as variables. The parametrical model of structure is established by the finite element software of ANSYS. Secondly, the structure robustness is based upon analysis from the robustness index, the reserve strength factor and the residual strength factor. The effects of three degradation rates of section properties, the established increasing rate of live loads and accidental loads on the robustness of bridges are considered. Finally, this method is used to analyze the time-variant robustness of Guotai Bridge located on the Haihe River of Tianjin. The results indicate that different degradation rates of member section properties have different effect on the robustness of Guotai Bridge, the effect of accidental loads has a close relationship with its acting position.