Abstract: Using Chl-a and its removal percent as indices, a self-made liquid ferment and raw water samples from a eutrophic ditch in which Microcystis aeruginosa the most dominant algae species were mixed by different volume fractions of the applied ferment to testify the control effect of the ferment on Microcystis aeruginosa being the most nuisance of blue algae in water environmental management and potable water treatment in the world. The results indicated:after mixed for 14 h, Chl-a concentration in all samples with ferment volume fractions varied from 2% to 10% could be reduced to some extent, and the sample with ferment volume fraction of 8% achieved the most favorable effect and its Chl-a removal percent was 53.17%. In the sample with ferment volume fraction of 8%,Chl-a concentration was continuously lowered with time extension, and its removal percent reached 78.77% after 62 h, but the Chl-a removal rate was abated with time. The dosing of the ferment acidified the samples.pH remarkably lowered with ferment volume fraction increase in samples when the dose was less than 8%.But whether ferment volume fraction in sample was 10% or 8%, pH was 3.2 and less than that of the ferment applied, which showed some changes had taken place in the mixed samples.The extension of mixed time of the sample with ferment volume fraction of 8% almost had no influence on pH except that pH was fallen to 3.1 after 36 h mixing.