Infrared solar spectra on clear days were measured automatically by an infrared solar spectrometer (ISS) with 0.4 cm 1 resolution developed by us. A line-by-line (LBL) computation method was used to calculate theoretical atmospheric absorption. In the wavelength range of 3. 410 -3. 438 μm, the absorption is mainly due to atmospheric methane and water vapor. Column atmospheric methane was retrieved from the recorded infrared solar spectra. The seasonal variation of column atmospheric methane in Hefei has been obtained from the measuremental data of nearly 18 months since the April of 1997, and found that it is similar to that of background data. The instruments; principles of measurement and some of results were introduced, and the results are also discussed briefly in the paper.