The invention discloses a nutritive growth-promoting disease-resistant pest-resistant drought-resistant water-retention bio-organic fertilizer and a preparation method thereof. The organic fertilizer is prepared by steps of airing and smashing sugar refinery filter mud, manioc waste, edible mushroom dreg, rubbish sludge, chicken manure and cow dung, adding water according to a weight ratio to adjust the water content to be 60%, adding enzyme strains, fully stirring and mixing, performing stack retting and fermentation, stirring piles for 4-5 times, spreading out and cooling when the organic matters are fully fermented without odor and with slight fragrance, preparing mineral elements according to a ratio, adding a water retaining agent, fulvic acid, shell powder, tea seed meal powder, and other plant disease-resistant pest-resistant agents, stirring, mixing and bagging. The bio-organic fertilizer is rich in nutrition and complete in function, and has a plurality of functions, such as growth promotion, drought resistance, water retention, disease resistance and pest resistance. The bio-organic fertilizer is capable of promoting balance and health growth of crops, reducing diseases, delaying senescence, increasing the output of the crops, improving the crop quality, improving the soil, enriching the soil fertility, reducing the cost and reducing pollutions.