Based on conventional observational data, NECP 1°×1° reanalysis data, and Lband sounding second data, two fog and haze cases occurred in 2013 are analyzed,including the circulation situation, diffusion conditions, and boundary layer characteristics. The results are as follows: the northwest flow and cold advection at 500 hPa, weak wind on the ground, updraftdowndraft distribution for vertical velocity, and inversion were the common features when fog or haze occurred. Northwest wind, cold advection at 850 hPa, shallow ground inversion (100 to 200 m), and thin wet layer corresponded with the haze. In contrast, east wind, warm advection at 850 hPa, deep suspended inversion (400 m) beneath 925 hPa, and thick wet layer corresponded with fog. The height of updraft was higher and the average intensity of inversion was stronger when the haze happened. The height of downdraft for the fog gone was lower and the intensity was weaker simultaneously. When the haze dissipated, the ground inversion almost had no change but for the fog, there were changes: bottomlifted suspension inversion and stable atmospheric stratification shifting to neutral. When the fog and haze disappeared, there were the following common features: downdrafts at upper levels reached at the ground; vertical wind shear increased and the dry air at upper levels with low dew point was transported to the ground.