In order to study the diurnal variation and seasonal characteristics of the atmospheric boundary layer structure in Suzhou, this study conducted continuous observation of aerosols detected by lidar from January to July 2014 The measurements of diurnal variation about extinction coefficient on 15 January, 16 March, 7 May, and 22 July 2014 are selected and the daily ABL heights by the optimized gradient method in this area are calculated. The correlation between ABL height and ground temperature & humidity is relatively high. The results show that the changes of the ABL height have a significant positive correlation with surface temperature and a negative relationship with the relative humidity, except for 15 January. Meanwhile, a joint study is conducted between the profiles of temperature and humidity data from the microwave radiometer and the profiles of extinction coefficient, and gained a good consistency between this two data.