NOVELTY - Use of Ganoderma lucidum solid residue for preparing dietary fiber comprising (1) inoculating Ganoderma lucidum strain containing residue into a production culture medium and then culturing at 25-30 degrees C for 15-30 days, where the culture medium comprises 8-45 pts. wt. of bagasse powder, 10-25 pts. wt. of bran, 1 pts. wt. of gypsum powder, 0.2 pts. wt. of magnesium sulfate, 30-80 pts. wt. of Ganoderma lucidum slag and 55-65% of water, (2) crushing and grinding the fermentation product and then adding distilled water carrying out ultrasonic extraction, is claimed.    USE - The Ganoderma lucidum solid residue is useful for preparing dietary fiber (claimed).    ADVANTAGE - The Ganoderma lucidum solid residue is utilized to prepare dietary fiber in a simple and cost effective manner with physiological activity and without wastage, toxicity and harmful substance.    DETAILED DESCRIPTION - Use of Ganoderma lucidum solid residue for preparing dietary fiber comprising (1) inoculating Ganoderma lucidum strain containing residue into a production culture medium and then culturing at 25-30 degrees C for 15-30 days, where the culture medium comprises 8-45 pts. wt. of bagasse powder, 10-25 pts. wt. of bran, 1 pts. wt. of gypsum powder, 0.2 pts. wt. of magnesium sulfate, 30-80 pts. wt. of Ganoderma lucidum slag and 55-65% of water, (2) crushing and grinding the fermentation product and then adding distilled water in the ratio of 1:5-15 at 70-90 degrees C, carrying out ultrasonic extraction for 0.5-2 hours and then filtering and collecting the filtrate and filter residue, (3) decompressing and concentrating the filtrate from 1/4 of the original volume to 1/2, adding concentrated solution with 95% ethanol in the ratio of 1:3-8 for 6 hours and then removing supernatant fluid, concentrating and spray drying the precipitate to obtain a water soluble dietary fiber and (4) filtering the material liquid obtained step (2) and then adding distilled water in the ratio of 1:12-18 and then adjusting pH value to 8-12, stirring in a water bath at 50-100 degrees C for 60-180 minutes, is claimed.