In general, ship structures are subject to impact loads, such as those caused by ship collisions, ice impacts, and aircraft landings. Impact loads are difficult to identify directly and accurately due to their short duration, high amplitude, and variable locations. This paper investigates the identification of impact loads in the time domain. Considering the group sparsity of impact loads and structural responses, three regularization methods are proposed to identify the impact load. A ship panel was chosen as the research subject to simulate the impact load. Based on the structural responses, the peak values and correlation coefficients of the identified loads are compared among the regularization methods to evaluate their accuracy and effectiveness. When a weakly noisy structural response is used as input, the proposed method can still effectively identify the impact load. The findings of this study can provide guidance for impact load identification in ship structures, supporting safety assessment and design basis.