Abstract: In order to implement deep removal of carbon and nitrogen from the mature landfill leachate, the combined process, which consists of an upflow anaerobic sludge blanket (UASB), an anoxic/aerobic reactor (A/O) and anaerobic sequencing batch reactor (ASBR) was used for landfill leachate treatment. Based on the coupling partial nitrification and anaerobic ammonium oxidation reaction, most of the organic compounds were degraded by UASB. The partial nitrification was achieved in A/O reactor. Deep nitrogen removal was carried out by anaerobic ammonium oxidation in ASBR. Results show that when the influent concentration of ρ(CODcr), ρ(NH₄⁺-N) and ρ(TN) are 2 220, 1 400-1 450 and 1 450-1 500 mg/L, the final effluent is 98, 7 and 25 mg/L with a total removal efficiencies of 95.6%, 98.3% and 99.5%, respectively. Efficient removal of COD, ammonia nitrogen (NH₄⁺-N) and total nitrogen (TN) is achieved by the process without the need of any external carbon source.