Abstract: To date,more than 100 taxa of genus Anabaena have been reported in the world,however,only about 40 species were described in China.Frequent occurrence of water blooms formed by cyanobacteria have become a serious environmental issue,but the information about water bloom forming Anabaena is quite limited,especially about the taxonomy of planktonic Anabaena species.During field investigations for water-blooms from many regions of China in the past years,a lot of samples were collected using the plankton net from a wide variety of habitats,such as lakes,rivers,ponds,streams and temporary water bodies.Targeting on water bloom forming Anabaena,single trichomes were picked with the pasteur micropipettes under a dissecting microscope from water samples into clear water,and washed several times,then cultured in a test tubes of CT medium under routine conditions with appropriate light intensity and temperature,and then many unialgal strains of planktonic Anabaena were finally obtained.The morphological characters of these Anabaena strains were examined using Olympus BX51 DIC microscope at magnifications of ?00 and ?00 connecting with a digital camera QIMAGING Micropublish 5.0 RTV.The results by morphological observation showed that eight species of Anabaena were new to China,and they were Anabaena affinis Lemmermann 1897,Anabaena planctonica Brunnthaler 1903,Anabaena kisseleviana Elenkin 1938,Anabaena aphanizomenioides Forti 191-,Anabaena bergii Ostenfeld 1908,Anabaena ucrainica(Schkorb.) Watanabe 1996,Anabaena oumiana Watanabe 1996 and Anabaena eucompacta Li et Watanabe 1999.Taxonomic features of these eight Anabaena species,including full morphological descriptions,photographs and comparison with the relative taxa,were presented in this study.