Abstract: Dual-comb spectroscopy (DCS) is one of the most promising technologies for ultra-long open-path multiple greenhouse gas detection. Ultra-long open-path DCS has the potential to realize horizontal open-path links over hundreds of kilometers and vertical open-path links between satellites and the ground base. Under these extreme detection conditions, identifying an appropriate wavelength band that ensures both technical feasibility and a reasonable absorbance for target components is critical but currently lacks studies. In this work, we simulate transmission spectra under different detection configurations to identify optimal wavelength bands for carbon dioxide (CO₂) and methane (CH₄) measurement. The simulation results show that the 1540 nm Watt-level high-power frequency combs developed are suitable for CO₂ measurement in both horizontal and vertical ultra-long detection configurations. The results also suggest that developing high-power fiber amplifiers for 1630 nm and 1636 nm will facilitate CH₄ measurement in horizontal and vertical ultra-long detection configurations, respectively. The amplification at 1636 nm will be a future research focus, as it is expected to enable simultaneous measurements of CH₄, CO₂, and water vapor in the vertical detection configuration.