Selecting a fine atmospheric site is very important for ground-based infrared astronomy. The sky background radiance and atmospheric transmittance are important factors for selecting site. Combined observations of solar spectral extinction and forward angular scattering were presented with ground-based FTIR on Yangbajing, Tibet. The direct solar irradiance and atmospheric background radiance were showed on 8-14 μm band. According to the atmospheric parameters, the direct solar radiance, atmospheric spectral transmittance and background radiance of selecting sites were compared by CART on long-wave infrared band. These will be useful to select a site for ground-based infrared solar telescope.