A novel system coupling an up-flow anaerobic sludge blanket(UASB) and sequencing batch reactor(SBR) was introduced to achieve advanced removal of organic and nitrogen from ammonium-rich landfill leachate. UASB could remove 88.1% of the influent COD at a volumetric loading rate of 6.8 kg COD·m-3·d-1. Nitritation–denitritation was responsible for removing 99.8% of NH+4-N and 25% of total nitrogen in the SBR under alternating aerobic/anoxic modes. Simultaneous denitritation and methanogenesis in the UASB enhanced COD and TN removal, and replenished alkalinity consumed in nitritation. For the activated sludge of SBR, ammonia oxidizing bacteria were preponderant in nitrifying population, indicated by fluorescence in situ hybridization(FISH) analysis. The Monod equation is appropriate to describe the kinetic behavior of heterotrophic denitrifying bacteria,with its kinetic parameters determined from batch experiments.