In order to reduce the excessive analysis frequency when analyzing and optimizing the impact load generated by the collisions with other ships on offshore floating devices, a shock load reconstruction method based on Genetic Algorithm (GA)-optimized Variational Modal Decomposition (VMD) and Shock Response Spectrum (SRS) is adopted. Aimed at the specific impact response signal, the GA is used to optimize the VMD parameters, and the impact load is decomposed. The cut-off frequency is determined by comparing it with the original load impact spectrum. Through the calculation of structural dynamic response, the impact load reconstruction method based on GA optimized VMD method and impact spectrum can reliably reconstruct the impact load before the structural dynamic response.