Abstract: The study of acidity (pH 5, pH 6), neutrality (pH 7) and alkalinity (pH 8—10) conditions on the type of fermentation, maximum concentration of total VFA and major acids, VFA distribution，yields and the production rates of total VFA and acetic acid from the textile dyeing sludge by anaerobic fermentation were investigated, and the mechanisms of the alkalinity condition beneficial to producing the organic acids were revealed. The results showed that acetic acid-type fermentation was the main type at different pH, but a lower pH was in favor of the accumulation of butyric acid. The concentrations of total VFA and acetic acid increased with increasing pH. The alkalinity condition could promote production of VFA because a high pH could promote the degradation of organic matter, improve conversion efficiency and inhibit the degradation of organic acids. pH at 10 was the optimum value to reach the best total VFA and acetic acid production from the sludge. At that pH value, the concentrations of acetic acid and total VFA were 8.21 g/L and 14.08 g/L respectively. The yields of acetic acid and total VFA could reach 34.97% and 75.72% respectively. In addition, the rate of acetic acid and total VFA production could reach 2.41g/(L·d) and 3.48 g/(L·d), respectively; Meanwhile, when the pH was 6, butyric acid could reach the highest concentration of 1.89g/L, suggesting that the pH value at 6 is suitable for the butyric acid-type fermentation.