A Raman-Mie lidar (RML) has been developed for measuring the extinction coefficient, backscattering coefficient and lidar ratio of atmospheric aerosols. Planetary boundary layer (PBL) aerosols were investigated with the lidar system during summer and autumn, 2009 at Hefei area. Result shows that during the experiment, remarkable variety dose no exist in the vertical profiles of lidar ratio, which means vertical distribution of aerosols in the PBL has a uniform mixture state and the same microphysical properties. Average value of lidar ratio is 64.4±6.1 sr in summer, which is a little higher than that in autumn with a value of 51.5±5.1 sr, this difference may caused by the change of particle component in the PBL,or the meteorologic factor. Lidar ratio does not change too much in the same season, especially in autumn. During the experiment, lidar ratio accumulated from 43 to 72 sr, with a mean value of 57.9 sr, which means particles in the PBL at Hefei area could be polluted continental aerosols.