Aerosol data measured by polarization lidar over Hefei in spring of 2005～2008 are analysed again. The observational results on Mar. 2nd, 2008 are used for case study and 137 samples of aerosol layers are investigated statistically. The results show that 70% of the average heights for these layers is ranged from 2 to 4 km, and the value of depolarization ratio for them, which is lager than 0.1, takes up to 85%, and these aerosol layers are sourced from the dust particles, which are transported in long range from the dust regions. These results can used to interpret why the aerosol concentration in free troposphere over Hefei in spring is higher than other seasons.