With the rapid development of the economy and the continued growth of vehicle ownership, the road pollution problem caused by vehicles is becoming increasingly serious, however, vehicle pollution is one of the main sources of PM2.5 in cities. Guangzhou, as an important economic development city in China, with a high concentration of pollution problems caused by emissions from traffic sources. Study on mitigating the hazards of urban road pollution is of great significance. The objective of this study is to investigate the contribution of green belts to the reduction of road PM2.5 in Guangzhou, which varies according to the intensity of motor vehicle emissions, road orientation, street aspect ratio and green belt planting type. Based on the research object of Guangzhou city roads, using the method of measurement and ENVI-met simulation. Firstly, the PM2.5 concentration distribution in urban road space and its influencing factors are measured and analyzed, secondly, validated the simulation software using measured data, finally simulated the PM2.5 reduction effect of different factors under the ideal road model, as well as simulated the PM2.5 reduction effect of different planting types of green belts. Results showed that:1) the distribution of PM2.5 concentration in urban road space was influenced by pollution sources, street aspect ratio, wind speed and wind direction, and green belt etc. Under natural abatement, it is mainly influenced by the double factors of wind speed and wind direction and height and aspect ratio. 2) Generally, it benefits for spread of PM2.5 in the road space with gradually increasing the street aspect ratio, as the rate of PM2.5 dispersion is increased. 3) The minimum distance of PM2.5 natural settlement in the space of main urban roads in Guangzhou was 12 m, an open and ventilated environment should be maintained within 0-12 m, with few ground obstacles. The key range of PM2.5 reduction was 12-24 m; within which ecological methods can be better used to settle particulate matter. 4) The reduction rate of PM2.5 was controlled by the green belt and the wind direction. Different green belt planting methods should be selected according to the dominant wind direction. The green belt on the parallel side and vertical windward side had positive PM2.5 effect, the recommended planting type was tree+tree irrigation grass, while on the vertical leeward side the green belt had negative effect, and the richer the planting type is, the more serious the PM2.5 gathering phenomenon becomes, the recommended planting type was tree+irrigation.