Sulfur dioxide(SO2) is one of the most common and important pollutant in the atmosphere. Differential absorption lidar (DIAL) measurement of SO2 has the advantages of high space-time resolution and high precision. Two laser beams, produced by two dye lasers pumped by two Nd:YAG lasers, were frequency doubled by two second-harmonic crystals, respectively. The dual wavelengths of λon=300.05 nm and λoff=301.5 nm were selected to probe atmospheric SO2. One beam of light was achieved by merging two laser beams via several mirrors, and this laser beam was expanded sixfold with a beam expander and then transmitted vertically into the atmosphere. Backscattered radiation of both wavelengths was received by the telescope and acquired by data acquisition unit. Based on the storage data, the vertical concentration profiles of SO2 can be inversion. Preliminary result during experiment shows that SO2 concentration is roughly from 0 to 14 ppb at altitude ranging from 0.3 km to 1.6 km over Dongpu island, west suburb of Hefei city. At last, four major measurement errors of this SO2 DIAL were analyzed and estimated.