The inhibiting effects and the correlative suitable condition of Effective Microorganisms (EM) on three common eutrophical algae are investigated through the cell liquid culture system. The results indicate that EM can have remarkable alga-inhibiting action against Chlamydomonas, Scenedesmus and Pediastrum by decreasing average percent of each algae biomass respectively to 46.80%, 99.07% and 97.17% when they are cultured 7 d jointly; that some factors such as culturing temperature, culturing time, casting quantity of EM and pH of culture medium...