Abstract: The dynamic response of the tubular cast steel T-joint under the impact load was investigated by using the nonlinear finite element method. The time-history curves of the impact load and the deformation of different cast steel joints were obtained. Three different deformations of cast steel joints were found including the pipe wall sag, the overall bending of the main pipe, and the axial deformation of the branch pipe. In addition, the relationship between the energy dissipation ratios of these deformations and the impact time was established. The research results show that the impact load and the maximum axial deformation of the branch pipe are related to the initial impact velocity at the same impact energy; the plastic energy consumption of joints increases with the growth of the diameter-thickness ratio of the main pipe, and decreases with the increase of the length-diameter ratio of the main pipe and the diameter ratio of the main pipe to the branch pipe. The deformation of the main pipe is larger than that of the branch pipe when the length-diameter ratio of the main pipe is small; and the pipe wall sag can be neglected when the diameter of the main pipe is close to the diameter of the branch pipe.