A lidar used for detection of extinction properties of aerosol in the troposphere at 1064nm are described. The extinction profile of aerosol varied with vertical altitude also are analyzed in terms of Klett inversion algorithm. Observed results over Suzhou city in summer in 2004 show that the extinction coefficient values of cloud are about three orders ofmagnitude larger than that in clear day in the same height. The height of aerosol boundary layer changes from 0. 75km to 2. 49km with a mean value of 1. 88km, and reachs the biggermena value of 2. 08km in August.