As an important part of territory virescence, road greening will promote social economy and eco-environment harmonious development. This study taked Populus tomentosa and Salix babylonica communities along Beijing Shunping Road(S305) in Shunyi County as research objects and analyzed light environmental characteristics indexes, such as Photosynthetic Photon Quanta Flux Density (PPFD), Gap fraction, Leaf Area Index(LAI), Mean Leaf Angle(MLA) and so on. The results showed that:(1)The total radiation and scattering radiation were basically same for the two communities, but the direct radiation and total radiation under the canopy decreased with DBH increasing. (2)The gap fraction of Populus tomentosa communities firstly decreased and then increased with DBH increasing, but it decreasd with DBH for Salix babylonica communities and the average of the latter was lower than the former. (3)LAI increased with DBH increasing for two kinds of communities, and the average of Salix babylonica communities was bigger. (4)The average of MLA was about 32° and decreased with DBH increasing for both kinds of communities. (5)Light extinction coefficient (k) showed that the Populus tomentosa had a relative higher ability of light interception. (6)And PPFD was closely related to MLA. According to the above results, we concluded that the light environment of Populus tomentosa communities changed larger apparently than that of Salix babylonica communities, and the latter was more suitable for establishing multi-layer vegetation system for road greening if light was the only factor taken into account.