The mechanical analysis of offshore floating devices is rigorous. If the impact load is not analyzed and optimized, its high cut-off frequency will bring great design difficulties to the follow-up design work. When analyzing the dynamic response of the piping system, the structural response results of the reconstructed impact loads with different cut-off frequencies are quite different. In this paper, the variational modal decomposition method (VMD method) is used to obtain the eigenmode functions of the shock load, the primary peak frequency of the corresponding frequency spectrum, and the maximum acceleration amplitude. And by selecting different cutoff coefficients, other impact loads can be obtained by reconstruction. Through numerical simulation research, it is found that when the cutoff coefficient is 0.01, the dynamic response of the reconstructed shock load is basically consistent with the dynamic response of the original shock load. On the premise of ensuring sufficient safety margin, the lower cut-off frequency can be obtained when the cut-off coefficient is selected as 0.2.