Plaaktothrix agardhii, a filamentous cyanohacterial species, is one of the major waterbloom-forming cyanobacteria and has been widely founded in lakes and reservoirs. However, its toxin-producing characteristics in the strains was never reported in China. In this paper, a strain Plaaktothrix agardhii SK3 was isolated from a reservoir of Guangdong Province and cultured in a gra-diem of light intensity and water temperature to investigate its growth characteristics. Results showed that 20p,mol/( m²·s) and 30% were optimal for its growth. The SK3 strain had microcystin synthetase gene-mcyE and was able to produce 0.06μg/mg(dry weight) microcystin-RR.