According to the water environmental physicochemical indices and Pseudoanabaena sp. monitoring data from May 2013 to June 2014 in the water transfer route of three important cascade reservoirs in a city in southern China, the characteristics of temporal and spatial distribution of Pseudoanabaena sp. were examined from biological and environmental perspectives, and the correlation between the cell density of Pseudoanabaena sp. and environmental factors was studied through correlation analysis. The results are as follows: (1)The cell density of Pseudoanabaena sp. has an obviously seasonal variation trend, which is significantly correlated with water temperature(P<0. 05). (2)The cell density of Pseudoanabaena sp. exhibits three types of distribution in the vertical direction: layer a>layer b>layer c; layer b>layer a>layer c; and layer c>layer a or b, respectively. (3)The cell density of Pseudoanabaena sp. increases significantly along the water transfer route of the cascade reservoirs. (4)The cell density of Pseudoanabaena sp. was significantly positively correlated with water temperature and total phosphorus(P<0. 05), and significantly negatively correlated with the ratio of TN to TP(P<0. 01).