The start-up and operational features of anaerobic ammonium oxidation（ANAMMOX）process were investigated comparatively in two 3.2 L upflow anaerobic sludge blanket（UASB）reactors，which both were fed with artificial waste-water composed of NH+4-N and NO-2-N at a proper ratio.The results showed that the removal efficiencies of NH+4-N and NO-2-N were 99.7% and 99.9%，respectively，in the No.1 reactor after 220 days; while the removal efficiencies of NH+4-N and NO-2-N reached 99.8% and 99.9%，respectively，in the No.2 reactor only after 150 days.The average ratio of removed NH+4-N，removed NO-2-N and generated NO-3-N was 1︰1.16︰0.15 at the stable phase in the No.1 reactor，while it was 1︰1.28︰0.15 at the stable phase in the No.2 reactor.The pH value had characteristic change in both reactors.The black activated sludge changed to yellow granular sludge in both reactors gradually.With the extension of time，the shock resistance of volume load was growing stronger and stronger in both reactors.Furthermore，UASB-ANAMMOX reactor with biofilm had the advantage of bacterial immobilization and keeping bacterial amount.