NOVELTY - Preparation of selenium-enriched bio-organic fertilizer comprises preparing fermented material, adding mixed microbial agents, fermenting, feeding in fermentation tank, controlling temperature at 60-70 degrees C and humidity of 70-80%, stirring for every 12 hours and standing for 3-5 days.    USE - Method for preparing selenium-enriched bio-organic fertilizer (claimed).    ADVANTAGE - The method is simple and has low treatment cost.    DETAILED DESCRIPTION - Preparation of selenium-enriched bio-organic fertilizer comprises preparing fermented material, adding mixed microbial agents, fermenting, feeding in fermentation tank, controlling temperature at 60-70 degrees C and humidity of 70-80%, stirring for every 12 hours and standing for 3-5 days. Fermenting material is composed of 50-60 pts. wt. livestock manure, 30-40 pts. wt. crop straw, 0.5-1 pt. wt. mixed microbial agents, 3-5 pts. wt. nitrogen, 4-6 pts. wt. phosphate, 3-5 pts. wt. potash, 0.5-1 pt. wt. selenium. Water content of livestock manure is 40-60% and pH value is 6.5-7.5. Crop straw is millet straw, corn straw, soybean straw, sorghum straw and/or rice straw. Carbon to nitrogen ratio is 40-50:1. Preparation of mixed microbial agents is carried out by mixing beer yeast bacteria, Bacillus subtilis bacteria, Lactobacillus delbrueckii bacteria, Streptomyces and Penicillium acid bacteria with volume ratio of 2-3:3-4:3-4:4-5:4-8 and carrying out fermentation of pure single-strain mixed microbial agent to obtain complex compound. Saccharomyces bacteria is obtained by preparing 10 g yeast extract, 20 g peptone, 20 g glucose and 100 ml distilled water, culturing at 28-38 degrees C and carrying out aerobic fermentation for 24-48 hours to obtain Saccharomyces bacteria. Bacillus subtilis bacteria is obtained by preparing 15 g peptone, 0.50 g beef extract, 20.0 g dextrose, 5 g sodium chloride and 100 ml distilled water, culturing at 30-36 degrees C and carrying out aerobic fermentation for 48-72 hours. Lactobacillus delbrueckii bacteria is obtained by preparing 70 ml wort, 10 g beef extract, 5 g yeast extract, 5 g soy protein powder and 1000 ml water with initial pH value of 6.5, culturing at 38-42 degrees C and carrying out aerobic fermentation for 48-72 hours. Streptomyces bacteria is obtained by preparing 1 g maltose, 1 g glucose, 1 g sucrose, 3 g soluble starch, 2 g peptone, 10 g beef extract, 5 g yeast extract, 2 g soy protein powder and 1000 ml water with initial pH value of 6.5, culturing at 30-35 degrees C and carrying out aerobic fermentation for 48-72 hours. Penicillium is obtained by preparing 3 g corn flour, 3 g soy protein powder, 3 g bran, 0.5 g peanut oil, 0.1 g magnesium, 3 g potassium dihydrogen phosphate and 1000 ml water with initial pH value of 6.5, culturing at 25-30 degrees C and carrying out aerobic fermentation for 48-72 hours.