The landfill of municipal solid wa ste (MSW) could be regarded as denitrification reactor and involved in ammonia nitrogen biological removal process. In this research, the process was applied to municipal solid wa ste collected in Shanghai, China, which was characterized by high food wa ste content. The NH+4 removal efficiency in the system of SBR nitrifying reactor followed by fresh and matured landfilled wa stelayer in series was studied. In the nitrifying reactor, above 90% of NH+4 in leachate was oxidized to NO-2 and 3 were removed in the way of denitrification proce ss in fre sh landfilled wa ste layer. At the same time, degradation of fresh landfilled waste was accelerated. Up to the day 120, 13615gCP (kgdry waste) and 1719gNP (kgdry waste) were converted from waste layer. It accounted for 50115% and 86189% of the total carbon and nitrogen content of preliminary fresh waste, which was 4142 times and 5117 times higher than that of reference column re spectively. After filtering through matured landfilled waste, BOD5 concentration in leachate dropped to below 100 mgPL, which would not affect following nitrification adversely. Because the matured landfilled waste acted as awell methanogenic reactor, 23% of carbon produced accumulatively from fresh landfilled waste degradation was converted into CH4.