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The characteristics of atmospheric particles in a lowvisibility event in Hefei is analyzed using high time resolution observations from 13 to 15 January 2013. Based on the data of visibility, relative humidity, and PM2.5 concentration, the process is divided into three stages:fog, mist, and haze, and thus the microphysical characteristics of atmospheric particles in different stage are studied. The results show that: The low visibility event experienced a conversion process of mist-haze-mist-fog-mist-fog-mist. PM2.5/PM10 and PM1/PM2.5 were negatively correlated with the visibility in whole process; PM2.5/PM10 was large in the fog stage, with fine particles accumulated faster; while PM2.5/PM10 was small at the mist and haze stages, with coarse particles generated faster. There was large difference in the spectral distribution of particles between different stages, and the number concentration, surface concentration, and volume concentration of fine particles had a similar spectral shape at mist and haze stages; the sedimentation effects were found from the number concentration, surface concentration, and volume concentration of particles with different size scales at the fog stage. The longer the fog stage lasted, the stronger the sedimentation effect of atmospheric particles.