In China, atmospheric mercury pollution is serious and is considered to be the largest mercury quantity emissions in world. Mercury can retain elemental form for a long time in atmosphere, and also can be transmitted for a long-distance. The feasibility studies of the differential optical absorption spectroscopy (DOAS) technology that applied for atmospheric mercury measurement were discussed. First, mercury resonance absorption is studied by the measurement of cells of mercury vapor with different lengths, then the absorption of saturated mercury vapor is analyzed using high-resolution spectrometer. Finally, with the current instrument, the concentration of mercury in air is measured. Through the experiment, main interfering gases are identified, and the requirement of the resolution of spectrometer is ensured. The research result provides advanced technical support for further measurements of mercury in the atmospheric and the mercury of high concentration in flue gas.