Abstract: In 1987 and 1988 we compared six strains of Anabaena in outdoor mass culture. The results showed that Anabaena sp. HB1042 and Anabaena sp. HB1105 have capabilities of stable production in the area around the middle and lower reachs of the Yangtze River, from the last tendays of May to the middle ten-days of September (123 days). The average effective growing days of HB1042 and HB1105 were 114 and 100, respectively. Average effective growing days of Anabaena variabilis HB1058, A. azotica HB686 and A. sphearica HB1017 were 73, 58, and 71 respectively. Adaptability of A. oryzae HB13 was relatively poor. Productivities of six strains of Anabaena were relatively high in the last ten-days of May, the first ten-days of June and July and the middle ten-days of August and Septeml er. Average biomass productivities of five strains of Anabaena (except HB13) were 10g (d. wt.)/m-2d-1. or near 10g(d. wt.)/m-2d-1.The six strains of Anabaena expressed their highest productivities in different periods. For this reason, the authors suggest that we can select different strains of Anabaena to obtain the maximum productivities according to seasonal conditions. Nutritional analysis showed that protein ontent of Anabaena spp. is 40％ amino acid composition is rational and essential amino acids are in accordance with the standard of FAO/WHO.