The invention relates to compound microecologics for purifying water quality and a preparation method thereof, belonging to the technical field of applied biotechnology. The method is characterized by conforming to the principle of diversified development of microecologics, utilizing various kinds of beneficial bacteria with different functions, carrying out scientific combination according to the proportion occupied by each kind of bacteria determined by orthogonal experiment, and forming efficient the multifunctional compound microecologics with the functions of intestine environment improvement, eating promotion, harmful bacteria restriction, water quality improvement, and the like. The invention is more characterized in that beneficial bacteria in the invention can be obtained easily at various parent strain markets, liquid fermentation technology is adopted for enlarging culture, and viable breeding accelerator, protective agent, viable absorbent, and the like are added to ensure the stability and the high efficiency of the compound microecologics. The invention solves the problems of unstable product characteristics, unsatisfactory using effect, low viable bacteria survival rate, and the like of microecologics at the current market.