Abstract: In order to explore the response mechanism of urban forest stands to the interaction between NAI and O₃, the concentrations of NAI and O₃ in different plant configurations are monitored in Beijing Nanhaizi Park by hand-held negative air ion(NAI) and ozone(O₃) analyzer, to compare the differences of NAI concentration in different stands. The results show that the interaction of NAI concentration and O₃ concentration can be regulated by different stands of urban forest. The diurnal variation of NAI concentration in different stands of urban forest is single peak and single valley type, while the diurnal variation of O₃ is single peak type. The variation of NAI concentration in different stands is as follows: the concentration of multi-layered forest is higher than that of pure forest, the concentration of coniferous forest is higher than that of broad-leaved forest, and the concentration of NAI in vegetated area is higher than that in non-vegetated area; the concentration of O₃ has different trends. The concentration in non-vegetation area is higher than that in vegetation area, the concentration in stratified forest is higher than that in pure forest, and the concentration in broad-leaved forest is higher than that in coniferous forest. From August to October, NAI and O₃ concentrations are negatively correlated in different plant stands, and each plant configuration have a certain regulatory effect on the interaction between them, with different differences. The interaction effect between NAI and O₃ concentration of plants such as Pinus tabuliformis, Pinus bungeana and Platycladus orientalis is strong.