Wind, as one of the important elements of urban microclimate, plays a crucial role in the dispersion of air pollutants. Adequate improvement should be made to mitigate the impact of urban spaces on the wind environment. Green spaces along pedestrian streets are an essential component of the public activity space system, accommodating most outdoor communication activities for citizens. However, the design of existing green spaces along pedestrian streets is often based on past experience, lacking empirical research on the relationship between green spaces, wind environment, and pollutant dispersion. Therefore, the correlation research between tree array space and PM2.5 pollutant distribution in the air, and how to optimize the layout of tree array space by design means according to its distribution regularities, are the main research contents presented in this paper. Taking two important green spaces in Jiefangbei pedestrian street of Chongqing as the sample points for research, this paper adopts the methods of measurement and numerical simulation. Firstly, the pollutant concentration and wind environment in the green space are measured and analyzed, and then use the PHOENICS tool to simulate and compare the wind environment of the green space in the study area before and after optimization design. The results show that the concentration of pollutants is usually high in green space as the greening has aggregation of pollutants to itself; An obvious negative correlation is found between wind speed and the concentration of pollutants, good ventilation is an important means to alleviate the air with low quality; Reasonable design of tree array space based on microclimate can effectively improve the air quality in local space.