The invention provides an active biology growth promoter and a preparation method thereof. The active biology growth promoter comprises the following components as mass percent: 1 percent of compound bacteria preparation, 5-6 percent of biogas digester waste liquid, 1-3 percent of citric acid fermentation liquid, 1-2 of percent biological humic acid, 1-2 percent of brown sugar and the allowance of water. The method comprises the steps as follows: mixing the biological humic acid, the brown sugar and some water; heating the solution for dissolution, and adding the rest water in the solution after the temperature is stable, and then obtaining a mixture through cooling; uniformly mixing the mixture with the mixture of the biogas digester waste liquid and the citric acid fermentation liquid, then adding the compound bacteria preparation; and stirring uniformly the mixture, and carrying out anaerobic fermentation to obtain the active biology growth promoter. The active biology growth promoter has the functions of regulating and promoting the plant growth and strengthening the photosynthesis and resistance of the plant, has effects of nutrition, disease resistance, and production increasing, is favorable for improving soil structure so as to form a benign soil ecological environment, and has the advantages of long shelf life, sufficient delayed effect, and obvious effects.