The invention discloses a method for purifying 
long chain dicarboxylic acid in 
fermentation broth. The method comprises the following steps: (I) adding 
inorganic salts and an alkali solution into 
fermentation broth, and stirring to dissolve the 
inorganic salts, wherein under the synergistic effect of alkali and salts, the 
cell wall of 
bacteria are dissolved, broken, and demulsified; (II) allowing the 
system to stand still to carry out layering, removing 
solid impurities such as bacterium dregs, and recovering 
alkane; (III) adding a proper amount of polyglycol into the 
fermentation broth, and dissolving the 
polymer to prepare a dual water phase 
system; (IV) subjecting the obtained dual water phase 
system to a super gravity treatment, wherein after the super gravity treatment, the upper phase and the lower phase are rapidly separated, proteins and pigments are dissolved in the upper phase, and the product (dicarboxylate salts) is dissolved in the lower phase; and (V) acidifying the lower phase obtained in the step (IV) to precipitate 
dicarboxylic acid crystals, and performing cooling, filtering, 
water washing, and 
drying to obtain a refined 
dicarboxylic acid product. A dual water phase extraction technology and a super gravity technology are combined to refine 
long chain dicarboxylic acid, the technical flow is shortened, the investment of equipment, time, and energy is saved, and the refined product has the advantages of high purity and low content of 
total nitrogen.