Abstract: The effects of cyanobacterial growth by UV-C photocatalytic oxidation with nanometric TiO₂ were studied.Analyzed from the physiological view point of Anabaena sp.PCC 7120,under UV-C photocatalytic oxidation with nanometric TiO₂,as indicated by increased the contents of reactive oxygen species of the O₂,·OH and H₂O₂,decreased the capacity of antioxidant system of the CAT,POD,APX and SOD,and decreased the contents of the soluble protein,C-PC,C-Chl a and C-Carotenoids.Furthermore,the results compared with those without photocatalytic,as indicated by reduced photosynthetic rate and photorespiration rate rapidly,decreased nucleic acid contents as for cell proliferation,and gained about 100% mortality.Observed under the light microscopy cell morphology was changed obviously.So UV-C photocatalytic oxidation with nanometric TiO₂ could achieve a good effect in photocatalytic restraint cyanobacteria.