In this paper, the dynamic behavior of square plates with various thicknesses and stiffening configurations subjected to underwater explosion (UNDEX) are evaluated through a relatively novel approach which is called Incremental Explosive Analysis (IEA). The IEA estimates the different limit-states and deterministic assessment of plats’ behavior, considering uncertainty of loading conditions and dynamic nature of explosive loading. In this new approach, intensity parameter of explosive loading is enhanced in an incremental manner and response of the target plate is recorded for every depth-stand-off loading condition. Then, the multi IEA curves are derived from several simulation results. The fractiles method is employed to summarize large amount of IEA curves’ data in a predictive mode. In addition, some summarized damage probability indicators such as fragility curves are extracted that provide useful information for quantitative damage analysis of plates in UNDEX loading. Results show that the IEA is a promising method for performance-based assessment of marine structures subjected to UNDEX loading.