The differential absorption lidar (DIAL) is a powerful and convenient tool for detecting the atmospheric trace gases. Based on dual wavelength differential absorption principle, we develop a set of lidar for measuring the concentration and distribution of the atmospheric SO2. This paper introduces the software, hardware and specific parameters of each subsystem in detail, then horizontal and vertical azimuth detection results are given. This lidar system adopts two tunable narrow linewidth dye lasers which pumped by Nd:YAG lasers, and produces l 600.10nm laser and 603.00nm lasers alternately. The lasers are frequency doubled by two second-harmonic crystals respectively and marked as λon=300.05nm and λoff=301.50nm which corresponds the strong absorption wavelength and the weak absorption wavelength of SO2 absorption spectrum. They are merged into one beam, and then expanded twelve times, and transmitted into the atmosphere coaxially with telescope finally. The back scattering signals are received by telescope system and converted into electrical signals by photomultiplier tube (PMT) after being collimated and filtered. These electrical signals are obtained by A/D acquisition card and stored in the computer for retrieving the concentration and distribution of the atmospheric SO2. Some field experiments are conducted in Huainan Atmospheric Science Research Institute, and we get some satisfactory results. On June 28th, 2016, the mean concentration of atmospheric SO2 is about 3.7 ppb in the range from 0.8km to 3.0km in horizontal azimuth. It conforms with the result of ground instrument from meteorological department. The vertical orientation detection is also performed at night of June 28th, 2016, and the atmospheric SO2 fluctuates in 0-5ppb which mainly exists below 1.5km.