In this study, effects of antimony Sb(V) on growth, pigments content, oxygen evolution, and photosystem II (PSII) activity of Microcystis aeruginosa were investigated. JIP-test, Q (A) (-) reoxidation kinetic test and S-state test were used in this study to study the energy distribution and electron transport in PSII. Treatment with Sb(V) at various concentrations ranging from 5 to 100 mg/l had long-term effects on growth, pigments content, and oxygen evolution of M. aeruginosa. Low concentration of Sb(V) had no significant inhibition of the biomass production and PSII activity but inhibited the pigment synthesis. Growth, pigments content, oxygen evolution, and PSII activity were seriously inhibited when treated by high concentration of Sb(V) (100 mg/l). The target sites of Sb(V) toxic effect on the PSII of M. aeruginosa were mainly on the donor side and the apparatus in the light-dependent reaction. The quantum yield for photochemistry, density of reaction centers and photosynthesis performance index decreased, whereas the dissipated energy increased. PSII activity of M. aeruginosa was promoted when exposure to 50 mg/l Sb(V) by increasing the density of active reaction centers and electron transport after Q (A) (-) .