Abstract: Micro-nanobubbles have the characteristics of small bubble particle size, large specific surface area, high dissolved oxygen concentration, long residence time in water and high mass transfer efficiency. Therefore, they have a good application prospect in the field of in-situ remediation of organic pollutants in groundwater. A simple landfill in the south of China was selected as the test site, and the micro-nanobubble preparation and injection integrated device was used to study the effects of process conditions such as extraction synergy, injection flow and injection duration on the mass transfer of oxygen micro-nanobubbles and the degradation and remediation of groundwater pollutants. The test showed that compared with ordinary air aeration, the oxygen concentration peak of oxygen micro-nanobubbles in water was higher and lasted longer. The extraction could significantly improve the mass transfer efficiency of micro-nanobubbles, enhance the influence radius and strengthen the degradation and removal effect of pollutants. Under the condition of multi-round injection-extraction combined processes, the injection influence radius could reach 4 m, with the removal rate of COD and NH₃-N reaching 96.1% and 92.4%, respectively. However, there was a certain rebound after the injection was stopped.