Revealing how spatial distribution patterns of forest and grassland affect ecosystem functions (EF) and hence control air pollutant (AP) concentrations is a key precondition for the development of ecological spatial layouts. However, there are not enough large-scale studies analyzing this interaction. Firstly, this study is based on the topological properties of forest and grass spatial distribution patterns to establish the relationship between EF and AP. The EAsim (Vegetation patterns-Ecosystem function - Air pollutant Simulation) model was then constructed to simulate the effects of changes in spatial distribution patterns of forest and grass on EF and AP concentration. The results showed that the spatial distribution of the forest and grassland on the Mongolian Plateau (MP) exhibited four basic patterns. Among them, the Core-Linked Ring pattern (CLR) accounted for the highest proportion of 40.74% and showed the highest stability. When all the spatial distribution patterns of forest and grass in the region are in CLR pattern, the water use efficiency of vegetation in the region will be increased by 39.60%, the wind and sand control function will be enhanced by 7.74%, while the concentration of AP will be reduced by 22.21%. The study confirms that by adjusting the distribution pattern of forest and grassland sources, the EF can be effectively enhanced and the concentration of AP can be reduced. This finding may provide a strategy for the enhancement of EF and management of AP in arid and semi-arid regions.