For monitoring the emission of CO2 in the global scopes, determining the location of carbon sources and sinks, high precision detection of the column concentration of atmospheric CO2 is needed. First, the principle of remote sensing of the column concentration of atmospheric CO2 is introduced, and the relationship between detection accuracy, spectral resolution and the required signal to noise ratio (SNR) is analyzed by using the lineby-line radiative transfer model (LBLRTM). Then based on satellite remote sensing requirements, the indexes of the optical system are analyzed. According to the indexes, echelle immersion grating is chosen as light splitting element, the inverse Cassegrain telescope and the off-axis three-mirror anastigmat structure beam splitting system is determined. The optical system of atmospheric CO2 column concentration detection imaging spectrometer with F number 4 and spectral resolving power of 21000 is designed. This optical system consists of a single telescope, a set beam splitting system and three pieces of focal plane array which has small size and good image quality.