Abstract: To explore the spatial and temporal dynamics of negative air ion provision and the influencing factors in the Green Belt Areas of Beijing, this study used in-situ monitoring records to quantitatively examine the provision capacity of negative air ions during the vegetation growing seasons. It also analyzed the effects of meteorological factors and vegetation communities. The results showed that: (1) During the growing season, the concentration of negative air ions generally displayed notable diurnal variations, peaking at around 14:00. In 2022, the total negative air ions provided by local forest plant communities in the Green Belt Areas reached 3.02×10²¹ ions, with supply capacity of 0.51×10¹⁶ ions/m². The second Green Belt areas significantly outperformed the first in both supply capacity and scale of negative air ions, primarily due to differences in forest area proportion and vegetation communities. (2) The concentration of negative air ions was mainly affected by temperature during the growing season, showing a significant negative correlation, particularly in the second Green Belt Areas, while the effect of relative humidity was insignificant. (3) Vegetation community factors had a significant impact on negative air ion concentration. Vegetation coverage, forest stand stage, and community structure were the main influencing factors, all showing significant positive correlations. The concentration levels of negative air ions varied significantly across different vegetation community factors, following this order: near-natural forest > artificial forest, mixed forest > pure forest, conifer-broadleaf forest > broadleaf forest > coniferous forest, and arbor with shrubs and herbage > arbor with shrubs > arbor > arbor with herbage. This study revealed that conifer-broadleaf forest with shrubs and herbage provided the highest concentration of negative air ions, while coniferous forest with herbage provided the lowest. In the future, efforts should focus on strengthening the construction of near-natural forests and creating mixed, multi-layered, and multifunctional forest communities. In the first Green Belt Area, adjustments in stand types and community structure are essential, while in the second Green Belt Area, optimization of community type and structure, as well as improvements in vegetation coverage, should be prioritized.