A mobile lidar system was developed which can be used to measure the lower layer atmospheric SO2. The lasers with wavelength of 300.05 nm and 301.50 nm are adopted in this system. The laser beams, produced by two narrow linewidth dye lasers pumped by two Nd: YAG lasers, are frequency doubled by second harmonic generation crystals. They are merged, expanded and transmitted into the atmosphere coaxially with telescope. The back scattering signals are received by the Newton telescope and converted into electrical signals by photomultiplier. The data are obtained by A/D acquisition card and used to estimate the profile of sulfur dioxide. The horizontal detection were field experimented in Huainan, the results show that the mean concentration of atmospheric SO2 is about 20 μg·m-3 in the range from 0.8 km to 3.0 km. It conforms with the results of ground instrument from meteorological department whose results is about 18-22 μg·m-3.