Abstract: ObjectiveThe present study explored the effects of exogenous salicylic acid on growth and photosynthetic system of Microcystis aeruginosa,in order to provide basis for application of salicylic acid in algaecide research and development.MethodThrough artificial culture,M.aeruginosa was treated with salicylic acid at different concentrations (0.02,0.04,0.06,0.08,0.10 and 0.12 g/L).After that,growth inhibition rate,chlorophyll a,phycobiliproteins and total soluble protein content in M.aeruginosa were detected by spectrophotometer and various reagents and kits.ResultThe higher the concentration of salicylic acid Nas,the more obvious the inhibitory effect on M.aeruginosa.When the concentration of salicylic acid was 0.12 g/L,the inhibitory effect was the strongest,and the inhibitory effect enhanced as time extended.The inhibition rate reached 95.66% after 48 hours.After treated with 0.10 g/L salicylic acid,chlorophyll a,phycobiliprotein and total soluble protein of M.aeruginosa maintained at initial level.While 0.12 g/L salicylic acid could effectively inhibit chlorophyll a.The content of phycocyanin(PC) was decreased and content of allophycocyanin(APC) was relatively increased,but content of phycoerythrin (PE) basically maintained at initial level.ConclusionSalicylic acid inhibits the capture and absorption of light,and disturb component composition of phycobiliproteins by disturbing the composition of phycobiliprotein by inhibiting photosynthetic pigments of M.aeruginosa such as chlorophyll a,which results in inhibition of algae growth and even death.Therefore algae chlorophy Ⅱ a is an action site for salicylic acid inhibiting growth of M.aeruginosa.