As an important part of rock mass dynamics, the seismic dynamic failure of rock mass was short of study before. In this paper, the reason of this short is analyzed first. The seismic dynamic failure of rock mass is classified into 6 types of forms： landslide, rock avalanche, spalling, collapse, ground fissure and rock mass dynam-relaxation, among them the rock mass dy- nam-relaxation is an important factor for causing a lot of secondary geological hazards. According to the action manner of seismic dynamic loads, stress state and failure mechanism, the rock mass seismic dynamic failure is further divided, the earthquake landslide and non-earthquake landslide are differentiated. At last, the characteristics of the failure are discussed from its inhomogeneity, repeated failure, clustering, controlling by discontinuities, and universality.