Tunicata, belonging to Urochordata, is comprised of three classes: Appendicularia, Thaliacea and Ascidiacea, with the former two being planktonic while Ascidiacea benthic. This paper summarizes research status and progress on classification and ecology of pelagic tunicates in China and abroad, and introduces in detail the basis of classification, current status and trends in Appendicularia and Thaliacea research. Pelagic tunicates are an important group of zooplankton in the subtropic and tropic waters. Distribution and variation of their species richness and abundance are influenced by physical and biological factors. Pelagic tunicates play an important role in marine food web carbon cycle as they feed on bacterioplankton and pico- and nano-phytoplankton and meanwhile are preys for commercial animals.