Abstract: 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 m, 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 was obtained from the measurem ental data of nearly 18 months since April of 1997, and the seasonal variation was found to be similar to that of backg round data. The instruments, principles of measurement and some of results were introduced, and the results are also discussed briefly in the paper.