The results of calculating the atmospheric transmission spectrum and modeling lidar signals in the informative range of greenhouse gas sounding (CO2 and H2O) on horizontal tropospheric paths using the two-channel infrared lidar system under development are presented. It is shown that the lidar system operation spectral range of 4878–4894 cm–1 (2043–2050 nm) is preferable for simultaneous probing of CO2 and H2O. In this range, the level of lidar signals lies in the range of 10–6–10–10 W and exceeds the equivalent power photodetector noise. Based on the results of the calculations, the technical appearance of the developed two-channel infrared lidar system is determined.