The Raman-Rayleigh-Mie lidar (RRML) system in the Nanjing Comprehensive Observation Base of China Meteorological Administration is introduced. In order to get accurate aerosol data, we use the lidar signal from Mie channel of the lidar system to measure the aerosol in the northern suburbs of Nanjing. The extinction profiles at different weather conditions (sunny and cloudy) are obtained. The variation of aerosol with time and wind direction is analyzed. The stratus base height and extinction structure are observed. According to experiments in real time, the aerosol loading changes with time in the windy case. The measurement results indicate that lidar can be finely used in dectecting aerosol. Tropospheric aerosol loading varies with wind direction due to the geographic location of Nanjing. The aerosol optical depth in the whole year of 2011 first increased and then decreased and the maximum value occurred in September. The extinction structure in stratus could be symmetric or asymmetric. Aerosol at the boundary layer diffuses downward, at the same time the altitude of boundary layer keeps stable and extinction of aerosol at low-altitude increases. In this process, the optical depth of aerosol from ground to boundary layer remains unchanged.