NOVELTY - Preparing functional food by sterilizing culture medium taken in several flask, cooling medium, preparing 5x 5 mm slant culture, maintaining culture medium to obtain black fungus liquid shake flask strain, sterilizing liquid culture medium, cooling to room temperature, adding liquid shake flask strain, culturing, ventilating to obtain black fungus liquid submerged culture strain, mixing kudzu powder, wheat and water, sterilizing mixture, cooling to room temperature, adding inoculum, covering with plastic paper, fermenting, drying and crushing fermented product.    USE - The method is useful for preparing functional food (claimed) used for reducing blood pressure and as antioxidant.    ADVANTAGE - The method is simple, cost-effective, and environmentally-friendly, does not need strict aseptic condition and discharge water, and consumes less energy. The prepared food with light fruit flavor has 3-20 mg/g total flavonoids, 0.2-1.5 mg/g puerarin, 0.9-8 mg/g protein, 0-0.5% sugar, 1-15 mg/g polysaccharides and reducing sugar.    DETAILED DESCRIPTION - Method for preparing functional food involves (a) sterilizing 40-150 ml culture medium taken in several flask at 100-330 degrees C for 10-60 minutes, cooling the medium, preparing 5x 5 mm slant culture, and maintaining culture medium at 22-33 degrees C and 60-180 revolutions per minute (rpm) for 5-10 days to obtain black fungus liquid shake flask strain, (b) sterilizing 50-80 vol.% liquid culture medium at 100-120 degrees C, cooling to room temperature, adding 3-10% liquid shake flask strain, culturing at 22-33 degrees C, 0.03-0.08 MPa and 60-250 rpm, and ventilating at 1:0.3-1:1.2 volume per volume per minute (vvm) for 3-8 days to obtain black fungus liquid submerged culture strain, and (c) mixing kudzu powder, wheat and water in weight ratio of 1:0.5-2:1.5-6, sterilizing the mixture at 110-150 degrees C for 10-60 minutes, cooling to room temperature, adding 5-20% inoculum obtained in step (b), covering with plastic paper, fermenting at 22-33 degrees C and 55-90% relative humidity for 5-20 days, drying and crushing the fermented product.