The invention relates to a method for extracting dietary fibers, in particular to a method for extracting dietary fibers from suaeda salsa. The method comprises the following steps: S1, collecting suaeda salsa residues, cleaning the collected suaeda salsa residues, drying the cleaned suaeda salsa residues, crushing the dried suaeda salsa residues, and screening the crushed suaeda salsa residues so as to obtain suaeda salsa reside powder; S2, weighing the suaeda salsa residue powder, adding sterile water, and performing flash extraction so as to obtain a solid-liquid mixture; S3, adjusting the pH value of the solid-liquid mixture, inoculating mixed microorganisms bacterial liquor a, and performing culturing so as to obtain fermentation liquor; S4, taking the fermentation liquor, adjusting the pH value of the taken fermentation liquor, inoculating mixed microorganisms bacterial liquor b, performing culturing, performing sterilization, performing cooling to obtain cooled fermentation liquor, and performing centrifugal separation so as to obtain upper-layer clear liquor and lower-layer precipitation; S5, taking the upper-layer clear liquor, adding anhydrous ethanol, performing standing, performing centrifugation, performing precipitation, and performing drying so as to obtain suaeda salsa soluble dietary fibers; and S6, taking the lower-layer precipitation, and drying the taken lower-layer precipitation so as to obtain suaeda salsa insoluble dietary fibers. According to the method disclosed by the invention, the dietary fibers are extracted by a fermentation method, reaction conditions are mild, the method is safe and efficient, the extraction rate of the dietary fibers is increased, the purity of the dietary fibers is improved, and the water-holding capacity and the swelling force of the dietary fibers are improved.