Impact experiment of a set of steel/RC composite beams was conducted. To consider the influence of local impact residual deformation, transient response was investigated using elastic-plastic contact law. Experiments show that the main failure mode is related to the value of potential energy of impacter and energy dissipation capacity of sand cushion. Each theoretical analysis result is slightly less than its corresponding experimental value. Experimental values and elastic-plastic contact analysis results present that the maximum displacement and the maximum steel strain on the lower layer at midspan increase with the thickness of sand cushion and the height of impacter.