NOVELTY - A biologically degradable oil dreg fertilizer (F1) is prepared by preparation of Bacillus subtilis fermentation liquor, Yarrowia lipolytica fermentation liquor, Geotrichum candidum fermentation liquor and Lactobacillus plantarum fermentation liquor. The method includes adding G. candidum fermentation liquor (80-110 pts. mass) and L. plantarum (90-120 pts. mass) fermentation liquor into treated oil dreg, and drying obtained fermented material by wind or fire until moisture is less than 20 wt.%, and obtaining powdered product.    USE - Method is used for preparation of biologically degradable oil dreg fertilizer (F1) (claimed) for promoting plant growth.    ADVANTAGE - The method has short treatment time of oil dreg, reduces environmental pollution, sufficiently utilizes specific nitrogen nutrient in oil dreg and obtains the fertilizer (F1) having output increase effect.    DETAILED DESCRIPTION - Biologically degradable oil dreg fertilizer (F1) is prepared by preparation of Bacillus subtilis fermentation liquor, Yarrowia lipolytica fermentation liquor, Geotrichum candidum fermentation liquor and Lactobacillus plantarum fermentation liquor. The method includes respectively choosing strains of 4 kinds of fermentation liquor including B. subtilis (10210), Y. lipolytica (1444), G. candidum (31418)A and Lactobacillus plantarum (6026); adding B. subtilis fermentation liquor (100-150 pts. mass) and Y. lipolytica fermentation liquor (100-150 pts. mass) into oil dreg (1000 pts. mass), adjusting moisture to 45-55 wt.% and pH to 6.5-7.0, mixing and controlling temperature of material at 35-40 degrees C, staying for 6-8 hours, filling steam and heating to 100 degrees C, and keeping heat for 25-35 minutes; adding G. candidum fermentation liquor (80-110 pts. mass) and L. plantarum (90-120 pts. mass) fermentation liquor into treated oil dreg, adjusting moisture to 45-50 wt.% and pH to 7.5-8.0, mixing, controlling material temperature at 35-40 degrees C, and staying for 4-6 hours to obtain fermented material; drying obtained fermented material by wind or fire until moisture is less than 20 wt.%, obtaining powdered product, or granulating obtained fermented material by conventional technique to obtain granular product.