In order to explore the algicidal performance and mechanism of a new kind of didecylγ-diquaternary ammonium salt(CP16)biocide,the removal effect of different dosage and light conditions on Microcystis aeruginosa and Chlorella pyrenoidosa were investigated.The mechanism of killing algae by CP16was analyzed and speculated by comparing with polyaluminum chloride.The results showed that when the concentration of CP16was 5mg/L,the turbidity of microcystis aeruginosa and chlorella pyrenoidosa reached the lowest value on the 7th day,and the removal rates were 50.91%and10.98%respectively,and the turbidity remained at a low level on the 15th day.When the dosage was 5—15mg/L,the OD420of microcystis aeruginosa and chlorella pyrenoidosa were lower than that of the initial blank one day later,and remained at a low value after 15days without increasing trend.The Chla removal rate of CP16to microcystis aeruginosa and chlorella pyrenoidosa was as high as 100%.After adding 5mg/L CP16,the inhibition effect of CP16on algae growth was better under the conditions of full light and dark 12h∶12hphotocycle,and the removal rate could reach 99%.CP16is a symmetrical cationic bisquaternary ammonium salt,which has the characteristics of water-soluble polyquaternary ammonium salt.CP16promotes the degeneration and death of algae cells through its special molecular structure,flocculation,adsorption and toxicity.The special structure of CP16makes it have strong killing activity,which can not only achieve the effect of killing algae,but also not form the effect of bioaccumulation.CP16has a good development prospect because of its good algae removal effect and special structure. [ABSTRACT FROM AUTHOR]