Abstract:Viruses existing in freshwater and seawater are called planktonic viruses (virioplankton). They are the most abundant biological group in the world’s oceans and lakes, and are a kind of significant strategic bio-resources. Recently, the viruses have been recognized to have significant roles in the control of harmful water alga blooms (red tide) and in the regulation of water ecosystems, and considered as a key nanoscale driver in the global biogeochemical cycle, especially in the global carbon cycle. Based on the progress review for their diversity, infection types, genome analysis, distribution and abundance in freshwater and seawater, and their ecological function of bio-pump, the research countermeasures and priority research orientations have been suggested in the paper. The authors further propose that the urgent affairs for contesting the significant strategic bio-resources should be to establish the technological platform for studying the freshwater and marine viruses.