Animal group in marine sediment is the important composition of marine ecosystem, and its diversity is the key to earth life-supporting system. However, the people knew little about this broad dark habitats and numerous animal group living in it. This paper discussed the current situation of animal diversity in marine sediment in terms of sedimental habitat, taxonomic category, body size, feeding behavious and ecological function,etc. It also discussed the important role acted by the animal diversity of marine sediment in the ecological course of ecosystem.The sediment environment in marine is various which provides the basis for animal diversity.In marine sediment, taxonomic categories of animal are various.There are not only great different on body size and feeding behaviours but also various functional
groups.Animal groups in marine sediment take part in material cycle,and the metabolism,transformation and transfer of pollutant.They also acts an important role in energy flow of ecosystem and transfer and stability of sediment.Finally,the measures for research and protection of animal diversity in marine sediment are proposed.