The L625 differential absorption lidar (DIAL) is introduced to measure vertical ozone profiles in the troposphere. System structure, measurement principle and data processing are also described. Comparison measurements of middle and upper tropospheric ozone are made with a couple of wavelength pairs of 289～299 nm and 289～308 nm at Hefei. Measurement results show that the differences between this couple is about 10%. Statistic errors below 10 km altitude are usually less than 2×1011 molecules per cubic centimeter in tropospheric ozone measurement by wavelength pair of 289～308 nm. Systematic errors due to aerosol loading are commonly less than 4%. Characteristics of seasonal variation of tropospheric ozone column contents from 5～15 km altitude are given and analyzed over Hefei. Maximal tropospheric ozone column contents occurred in the second quarter and minimal contents in the third quarter.