Abstract: The effect of biological nutrient removal depends on the quantity and activity of nitrobacteria in activated sludge and biofilm. At medium temperature range，the conversion of ammonia nitrogen into nitro nitrogen is mainly conducted by the medium temperature nitrifying bacteria. While，most of the medium temperature nitrobacteria are hibernated bellow 10 ℃ and lose their metabolic ability below 4 ℃，which resulted in the insufficient treatment for waste water can not reach the standards. In this study，cold-adaptive nitrobacteria were isolated by cultivating the activated sludge in low temperature（≤10 ℃）to make the cold tolerance nitrobacteria become the dominant bacteria，with which low-temperature-resistant nitrobacteria were constructed by using entrapped bioaugmentation technique and their effects for nitrogen removal were investigated.