Abstract: Oleic acid-coated nano-iron was used to remove NO₃^--N from groundwater in this study. The influences of DO concentration, light, temperature and initial pH on NO₃^--N removal efficiency were observed with sequencing batch experiments lab. The results indicated that the NO₃^--N removal rate by oleic acid-coated nano-iron was influenced by DO concentration. The NO₃^--N removal rates were 78.9% and 42.3% with the corresponding DO concentration of 0.50 and 5.41 mg/L respectively after 264 h. The NO₃^--N removal rate was 97.6% after 400 h, and there was little difference under natural light and dark condition. However, convert efficiency of NO₂^--N under dark condition was 1.57 times that of under light condition. These reactions were significantly affected by the temperature. The removal rate of NO₃^--N at 25 ℃ was 2.01 times that of at 15 ℃ after 48 h. The initial pH (pH = 4,7, 9) had no significant effect on NO₃^--N removal efficiency using coated nano iron. The NO₃^--N removal efficiencies in those three conditions were 87.9%, 84.5% and 82.3%, respectively after 400 h. The value of pH decreased at high pH condition, and increased at low pH condition in the process of reaction, and finally became stable at pH around 8. Therefore, groundwater environmental factors (temperature, anaerobic, dark) could influence the nitrate removal efficiency using coated nano iron. The simulation of groundwater environmental condition is necessary, and it could provide important reference for access of objective data in the future research.