With the development of urbanization, PM_2.5 pollution is prominent, more and more attention has been focused on PM_2.5 pollution in the cities.The research showed that urban trees provides an important ecological guarantee for the urban environment, plays an extremely important role in regulating, alleviating and reducing the urban PM_2.5 pollution hazards, and carries out the forward layout of urban trees by selecting tree species, optimizing the configuration structure and improving the quality of forest trees. However, how to further study the mechanism of PM_2.5 pollution regulation by urban trees and realize the maximization and optimization of PM_2.5 effect is still a problem to be solved.It is urgent to conduct the study of PM_2.5 effect in multi-scale and multi-dimensional, and further combine and extend in different scales and dimensions. In this paper, based on the field monitoring of the PM_2.5 capacity of urban trees regulation, the relevant literature regarding the PM_2.5 mechanism of urban trees regulation was summarized in terms of the unit leaf area and morphological characteristics, configuration structure characteristics, meteorological conditions and other factors. At the same time, the temporal and spatial characteristics of urban trees regulation PM_2.5 were concluded in terms of the temporal change characteristics, horizontal distance and vertical change characteristics, internal and external change characteristics of the PM_2.5 effect of urban trees regulation. Finally, the paper puts forward the main problems and future research prospects of PM_2.5 effect of urban trees regulation.