The invention discloses a preparation method capable of improving the clarification and the dietary fiber content of vinegar. The possibility of precipitation in a vinegar fermentation process is controlled in combination with a solid vinegar brewing process, and additional investment of equipment is avoided. In different processes of vinegar production, an enzyme preparation and soybean polysaccharide are separately added to reduce the possibility of vinegar precipitation: in the early stage of fermentation, the enzyme preparation is added during the production of solid vinegar to decompose unfermented starch, protein, cellulose and other substances, so as to reduce the precipitation in vinegar; then after the vinegar is boiled, that is, the Maillard reaction occurs, the soybean polysaccharides is added to stabilize macromolecules in the system and prevent macromolecule aggregation, thereby reducing precipitation in vinegar products; and the dietary fiber content of soluble soybean polysaccharide exceeds 60%, which can increase the dietary fiber content of vinegar products.