The airflow and particle deposition within an isolated street canyon were studied numerically.In the numerical simulation,the low or medium wind speed (3,5,10 m/s) as well as the high wind speed(20 m/s)were adopted and particles with the diameter in the range of 0.01~10 μm were considered.The airflow fields,particle trajectories and particle deposition efficiencies on various building surfaces and on the street floor were all obtained.It is revealed that:the particle deposition efficiency on the street floor is obviously higher than that on building surfaces;the deposition efficiencies on the leeward and windward walls,building roofs and on the street floor are all insensitive to the particle size under a fixed wind velocity and insensitive to the wind velocity under low or medium wind speed;on the windward wall and the road surface,the particle deposition efficiency under high speed is apparently greater than that under low or medium wind speed,whereas on the leeward wall and the building roofs the particle deposition efficiency under high wind speed in obviously lesser than that under low or medium wind veloccity;the deposition efficiency on the leeward wall is greater than that on the windward wall under low or medium wind speed whereas the deposition efficiency on the leeward wall is lesser than that on the windward wall under high wind speed.