Pyroclastic rock is a direct product of explosive volcanic eruption. The different clast composition, particle size and texture reflect the dynamic process of different lithofacies. The study on petrology and lithofacies association of pyroclastic rocks has developed into the modern volcanological research represented by physical volcanology. As a collection of pyroclastic materials, pyroclasts of different genetic types can directly correspond to the characteristics of dynamic parameters for different volcanism stages. The three fundamental types of pyroclastic deposits are air fallout, pyroclastic flow, and pyroclastic surge. The fragment process of a volcanic eruption mainly involves the dissolution of volatiles, the magmatic fragmentation and the breaking process within different volcanic flows. For the direct products of magmatic, phreatomagmatic and phreatic eruptions, the pyroclastic rocks are composed of the cognate fragments from depth, the accessory fragments trapped from the conduit, and the accidental fragments captured by volcanic fluids flowing on the surface. Pyroclasts are defined as the direct behavior products of explosive eruption. But volcaniclastics refers to the fragments that are produced by autogenic and quenching processes of a lava flow, or by the epiclastic fragmentation from degradation including masswasting, avalanche and lahar. The establishment of volcanic lithofacies models laid the foundation for the transition to the stage of volcanology in the late 1980s. On the basis of geological research, the empirical model, experimental simulation and numerical simulation of the process and control mechanism of volcanic activity are explored. Among them, the intervention of fluid dynamics is of milestone significance in promoting the understanding of the basic processes of volcanic eruption. The resulting volcanology is the study of volcanoes and their constructing mechanism, eruptional process and the product characteristics.