Based on the principle of simultaneously nitrifying-denitrifying nitrogen removing, sewage treatment plant wastewater sludge was used as inoculum, and the continuous low temperature shaker was used to enrich the simultaneously nitrifying-denitrifying nitrogen removing bacteria (SNDB-5) at 15℃. Traditional and modern molecular biology methods were adopted to determine the taxonomic status of the isolated bacteria which was named SNDB-5. Water bath shaker was used to analyze the NO2 --N removal in the nitrifying bacteria culture medium. The results show that SNDB-5 has 99.0 % homology with Pseudomonas mendocina. Morphological, gram staining and biochemical characteristics are also similar to Pseudomonas mendocina. Incubating reaction conditions in shaker shows that SNDB-5 activity is inhibited when the concentration of NO2 --N increases to 150 mg/L.