The　road　green　belt　can　affect　the　convective　flow,　heat　and　mass　transfer　in　the　street　canyon.　The　CFD　technology　coupled　with　porous　media　model　was　applied　to　investigate　the　effects　of　the　different　road　green　arrangement　patterns　on　the　convective　heat　transfer　and　vehicle　exhaust　pollutant　diffusion　in　the　street　canyon　with　W/H　=　1　:　2.　By　analyzing　the　flow　structure,　temperature　and　pollutant　distributions　under　different　cases,　it　was　found　that　the　ventilation　in　the　street　canyon　would　be　enhanced　by　the　mixed　flow　(Ri=0.47)　due　to　the　heating　ground,　but　not　significantly.　The　roof　greening　can　reduce　the　flowing　air　temperature　and　enhance　the　convection　in　the　street　canyon,　but　which　also　can　cause　the　inflow　velocity　to　get　smaller　and　deteriorate　the　ventilation.　In　addition,　the　increasing　green　belts　will　reduce　the　ambient　temperature　in　the　street　canyon　significantly,　but　also　obstruct　the　airflow　more　sharply.　Furthermore,　it　reduced　the　average　velocity　in　the　street　canyon　to　increase　the　high　concentration　area　of　pollutant　CO.　©　2019,　Science　Press.　All　right　reserved.