Abstract: A general approach based on the energetic fragmentation criterion inspired by Grady is considered. Starting from size distribution of fracture advised in our early research, mass distribution law is derived for dynamic failure process in liquid metals. This approach is also discussed and compared with experimental observation of dynamic fragmentation in melted state of laser shocked-loaded tin, and the theoretical curves can give a good comparability with experimental distribution. Further, the major causes of discrepancy between theoretic predictions and experimental observations are discussed, and further work is needed to better understand the evolution of this microspall process.