Abstract: The nitrogen removal performance of an ANAMMOX-UASB-biofilm system was comparatively investigated in two up-flow anaerobic sludge blanket (UASB) reactors, one of which was fed with mature landfill leachate polluted water, and the other one fed with inorganic polluted water. ANAMMOX, nitrification, denitrification activity and physical-chemical characteristics of the ANAMMOX granular sludge were studied and contrasted. The results showed that a high nitrogen removal efficiency was achieved through coupling ANAMMOX and denitrification in the 1# system after continuous cultivation. In the stable stage, 86.66% and 76.77% of the total nitrogen on average were removed in the 1# and 2# systems respectively. ANAMMOX, nitrification and denitrification activity were observed in both the 1# and 2# systems. The ANAMMOX and nitrification activity in the 1# system was lower than that in the 2# system, whereas the denitrification activity in the 1# system was higher than that in the 2# system; the TN removal rates of ANAMMOX in the systems were 0.286 and 0.301 g/(g·d) respectively. The color of the granular sludge in the 1# system changed from brick red to red-brown, and the color of the granular sludge in the 2# system was brick red continuously. The size of the granular sludges in the 1# and 2# systems were mainly between 1.5 and 2.5 mm, and the weight proportions were 66.10% and 50.67% respectively, which were in the best mass transfer range.