Abstract: Take NO3^--N pollution of groundwater for example, the authors used a selected microbial pool agent and a little nutrient carbon to perform an experiment for in situ microecological remediation of NO3^--N-contaminated groundwater in the Hebei plain. The results indicate that the NO3^- concentration in groundwater decreases from 58-72.66 mg/L to 7.38-0.85 mg/L through 4.5-10 days of remediation experiment with the removal rate reaching 86.5-98.8%. The removal effect is good and lasted long. The technique provides a feasible technical support for the remediation and control of extensive NO3^--N pollution of groundwater.