Abstract: Large DNA viruses in freshwater ecosystems usually refers to the DNA viruses present in freshwater ecosystems, whose genome size is close to or more than 100 kb. They are usually pathogens that cause infections in aquatic organisms, including amphibians, fish, shrimp, cyanobacteria (blue-green algae) and so on. Viruses affect cultured aquatic animal health and freshwater ecological balance. The research trends and developments are summarized here. Primary literature focused on representative strains of several large DNA viruses in freshwater ecosystems, such as Rana grylio virus (RGV) and Andrias davidianus ranavirus (ADRV) in the family Iridoviridae, crucian carp herpesvirus (CaHV) in tne family Alloherpesviridae, Procambarus clarkii nimavirus (PCV) in the family Nimaviridae, and Microcystis aeruginosa myovirus isolated from Lake Dianchi (MaMV-DC) in the family Myoviridae. The development prospects of freshwater large DNA viruse research and aquatic virology was discussed in order to provide reference for relevant researchers.