Abstract: A high-efficient heterotrophic nitrifying bacterial strain named Ni3-1 was isolated from sewage ditches． Based on morphological observation and 16S rDNA sequence analysis，strain Ni3-1 was identified as Alcaligenes faecalis． NH + 4 － N removal characteristics of strain Ni3-1 was then analyzed． Ｒesults showed that heterotrophic nitrification by the strain Ni3-1 occurred mainly during its logarithmic growth phase． Carbon source had an obviously effect on NH+ 4 －N removal efficiency， and trisodium citrate and sodium succinate were the most appropriate ones． The strain exhibited appreciable heterotrophic nitrification activity when the NH+ 4 －N concentration was in the range of 10 ～ 1 000 mg /L． Strain Ni3-1 was active over a wide range of temperatures ( 25 ～ 35 ℃) ，pH values ( 6 ～ 9) and C/N ratios ( 10 ～ 25) ，and more than 95% of NH + 4 －N could be removed within 24 h under these conditions． Above all，this strain worked well when applied for pig wastewater treatment，and the NH + 4 －N removal ratio reached 93. 2% within 48 h． Neither of NO － 2 －N nor NO － 3 －N was detected in the treatment process． Heterotrophic nitrifier Alcaligenes faecalis Ni3-1 had high efficiency in NH+ 4 － N removal and had potential for treating wastewater with a high NH+ 4 －N load．