In order to study the characteristics of cirrus,high-altitude cirrus clouds over Hefei,Anhui(31.90°N,117.16°E)were observed by L300 Mie lidar. These cirrus clouds were simultaneously detected when the lidar took regular nighttime measurements of tropospheric aerosol. The structures and optical properties of the cirrus clouds as well as their time variation are discussed and analysed. Our results show that the peak of cirrus over this area range mainly from 8 km to 11 km,and their structures change with season as well.