Abstract: Synechocystis sp. PCC6803 and Microcystis aeruginosa were treated with the dopant nano TiO2 components 1% Ag,5% Fe2O3, 10% ZnO, and nano TiO2 alone under natural illumination and fluorescent conditions . We determined the content of chlorophyll a, carotenoids, extracellular O2 -. and superoxide dismutase activity in samples. The natural illumination condition was more effective than the fluorescent condition in the photocatalysis of nanometer material. The dopant nano materials were more effective than nano material alone in inhibiting growth of blue-green algae, 1% Ag having the best inhibitory effect. M. aeruginosa has a stronger ability to adapt to superoxide anion stress produced by photocatalysis of nano TiO2 than Synechocystis sp.