In this study, long-term effect of organic matter strength on SNAP (single-stage nitrogen removal using anammox and partial nitritation) process treating high strength ammonia wastewater was investigated. The concentrations of ammonium andCOD (chemical oxygen demand) in the wastewater were 2,000±20 and 500-2,000 mg/L, respectively. Stable simultaneousnitrogen and COD removal were observed in theSNAP process with theTN (total nitrogen) and COD removal efficiencies of 92% and 80%, corresponding the loading of 0.5 kg N m-3 d-1 and 0.38 kg COD m-3d-1, respectively. This process may have applications for treating high strength ammonia and low C/N wastewater such as mature landfill leachate.