The invention provides a composite bacteria preparation used for disinfection. The composite bacteria preparation is composed of, by mass, 1 to 25% of a microbial community, 0.5 to 10% of a microbial nutrient solution, and 65 to 95% of bacteria normal saline. The microbial community with bacteria killing effect is taken as a main microbial community, the content of effective probiotics is capable of reaching 3*10<7> cfu/g; the main microbial community possesses killing, phagocytosis, and rapid lysis effect on pathological bacteria such as vibrio parahaemolyticus, aeromonas hydrophila, aeromonas punctata, escherichia coli, salmonella, and edwardsiella spp, so that the composite bacteria preparation is capable of reducing the content of pathological bacteria in water bodies obviously, killing bacteria with bacteria, and repairing water body microecological balance.