Abstract: Dry-spun acrylic fiber wastewater is a kind of recalcitrant wastewater with a variety of pollutants. At present, the acrylic fiber wastewater treatment processes applied in the Acrylic Fiber Plant of Fushun Petrochemical Corporation have several drawbacks, such as low nitrogen removal efficiency and high concentration of COD_Cr in the effluent. In this study, the membrane bioreactor (MBR) with packed type A/O process was applied in the treatment of dry-spun acrylic fiber wastewater. The removal efficiencies of COD_Cr, ammonia-nitrogen and total nitrogen in the treatment of dry-spun acrylic fiber wastewater by MBR and the stability of the reactor were investigated. The results indicated that the MBR technique had high resistance to shock loading of water quantity and water quality, and the water quality of the effluent was stable. The ammonia-nitrogen and total nitrogen removal rates could reach above 97% and 60% by A/O process. However, denitrification in the anoxic zone and nitrification in the oxic zone were limited by the deficiency of alkalinity and carbon sources due to bad biodegradability of dry-spun acrylic fiber wastewater and high concentration of ammonia-nitrogen.