In order to study backscattering and polarization properties of background aerosol over Hefei, routine observed data by polarization lidar in clear days from Jan. 1, 2007 to Feb. 2, 2009 are analyzed statistically. The results show that aerosol backscatter ratio and depolarization ratio in the middle and upper troposphere over Hefei vary obviously with season, the values of which are biggest in spring, take secondary place in winter, then in summer, least in autumn. In spring, the results show relatively larger values because of increased non-spherical particles. The analysis can provide useful reference for inversion of low troposphere lidar detection data and for research of aerosol layers (dust or pollution) in special weather conditions.