NOVELTY - Regulating mixed culture of microalgaes by Lactobacillus plantarum and for purifying the aquatic waste water through synergic action of Lactobacillus plantarum and microalgaes, comprises placing the microalgaes in a normal culture apparatus for mixed culture, adding Lactobacillus plantarum to regulate each microalgae in a balanced growth; subjecting to an amplifying culture; and maintaining the density of Lactobacillus plantarum in the amplifying culture tank to be 104 to 105 colony forming units/ml to purify the wastewater.    USE - The process is useful for regulating mixed culture of microalgaes by Lactobacillus plantarum and for purifying the aquatic waste water through synergic action of Lactobacillus plantarum and microalgaes (claimed).    ADVANTAGE - Through the direct or indirect action of Lactobacillus plantarum, the process regulates the quantity ratio of the microalgaes to keep each microalgae in balanced growth and good stability, to avoid singleness of the biological diversity of the microalgaes in the mixed culture system, and to avoid extreme advantage or disadvantage of a certain microalgae. Moreover, through the synergic action of Lactobacillus plantarum and microalgaes, the process can remove nitrogen and phosphorus from the aquatic wastewater.    DETAILED DESCRIPTION - Regulating mixed culture of microalgaes by Lactobacillus plantarum and for purifying the aquatic waste water through synergic action of Lactobacillus plantarum and microalgaes, comprises placing the microalgaes in a normal culture apparatus for mixed culture, adding Lactobacillus plantarum to regulate each microalgae in a balanced growth; subjecting to an amplifying culture until the biological total amount increases by 1-3; where the microalgaes will form together with the Lactobacillus plantarum to obtain a mixed biological liquid; introducing the Lactobacillus plantarum-microalgaes mixed biological liquid and the aquatic wastewater from the aquaculture pond into the amplifying culture tank, and maintaining the density of Lactobacillus plantarum in the amplifying culture tank to be 104 to 105 colony forming units/ml to purify the wastewater.