The study was carried out for the pretreatment of brewery wastewater to remove nitrogen efficiently using anammox reaction in the plant of Asahi Breweries, Ltd. Organic compounds were removed in the first aeration tank (effective volume 360 L) fitted with a thread type acrylic fiber biomass carrier, and the subsequent partial nitritation was successfully achieved in the same type of second aeration tank. A two-stage pretreatment system for anammox process was operated continuously for half a year and the results showed that 1.5-2.4 kgTOC/m(3)/d TOC removal rate was obtained in the first aeration tank and 1.5-2.5 kg-NH(4)/m(3)/d ammonia conversion rate was obtained from second partial nitritation reactor. Except sudden inflow of high concentrated wastewater or suspended solids and miss operation, pretreatment for anammox was achieved for a month in which 80% of organic carbon was removed and nitritation rate was approximately 50%.