NOVELTY - Separating butyric acid oxidized dominant hydrogen-producing acetogenic flora (A), by carrying out primary acclimation of anaerobic activated sludge, preparing bacterial suspension, carrying out enrichment culture of the concentrated bacterial suspension, preparing microbial composition of acetogenic flora (A) and methanogen, preparing acetogenic flora (A), culturing the acetogenic flora (A) in butyric acid culture medium, and repeating the culture process.    USE - The method is useful for separating acetogenic flora (A) (claimed) useful for treating organic wastewater.    ADVANTAGE - The method is easy and simple. The hydrogen production rate of the acetogenic flora (A) is 7-10 times of the hydrogen production rate of other hydrogen-producing bacteria. The acetogenic flora (A) degrades butyric acid of high concentration and improves treatment of high concentration organic wastewater.    DETAILED DESCRIPTION - Separation of butyric acid oxidized dominant hydrogen-producing acetogenic flora, involves (i) using soybean protein wastewater with chemical oxygen demand (COD) concentration of 2000-10000 mg/l as inflow water, using anoxic baffled reactor of four-celled chamber as model, and carrying out primary acclimation of anaerobic activated sludge for 48 hours at a pH (of the inflow water) of 7-7.5, and 35 degrees C, (ii) introducing nitrogen gas into a 120 ml sterile serum bottle filled with several glass beads, adding 30-60 ml of the acclimated anaerobic activated sludge of the third cell chamber, sealing the opening, and vibrating at 35 degrees C at a speed of 130 revolutions per minute (rpm) for 1-2 hours to obtain bacterial suspension, (iii) obtaining 10-20 ml of the bacterial suspension with sterile injector and then transferring into sterile serum bottle filled with butyric acid culture medium with mass concentration of 10000 mg/l, and carrying out enrichment culture at pH of 7-7.5, 35 degrees C and vibrating velocity of 130 rpm to obtain bacterial suspension after enrichment culture, (iv) transferring (when the mass concentration of the butyric acid in the butyric acid culture medium during the enrichment culture is less than 1000 mg/l) the concentrated bacterial suspension after enrichment culture into the butyric acid culture medium with a mass concentration of 10000 mg/l, and repeating enrichment culture at pH of 7-7.5, 35 degrees C and vibrating velocity of 130 rpm to obtain bacterial suspension after enrichment culture, (v) repeating the step (iv) for 5-7 times to obtain microbial composition of acetogenic flora (A) and methanogen, (vi) transferring the microbial composition into butyric acid culture medium comprising 0.1-10 mM/l of sodium 2-bromoethane sulfonate, culturing at pH of 7-7.5, 35 degrees C and vibrating velocity of 130 rpm to obtain acetogenic flora (A), (vii) when the mass concentration of the butyric acid culture medium comprising sodium 2-bromoethane sulfonate is less than 3000 mg/l, transferring the acetogenic flora (A) into butyric acid culture medium comprising 0.1-10 mM/l of sodium 2-bromoethane sulfonate and culturing at pH of 7-7.5, 35 degrees C and vibrating velocity of 130 rpm, and (viii) repeating the step (vii) for 3-6 times to separate the acetogenic flora (A), where the volume ratio of the bacterial suspension to the butyric acid culture medium in step (iii) is 1:8, the volume ratio of the concentrated bacterial suspension after enrichment culture to the butyric acid culture medium in step (iv) is 1:8, the volume ratio of the microbial composition to the butyric acid culture medium in step (vi) is 1:8, and the volume ratio of the acetogenic flora (A) to the butyric acid culture medium in step (vii) is 1:8.