This paper established a mathematical model to explore the characteristics of infrared energy of 8-14 gm emitted from an urban surface and analyzed the atmospheric transmittance under actual weather conditions. Then, the amount of infrared energy that penetrated the atmospheric infrared window was determined, based on the coupling analysis of urban radiation energy and atmospheric transmittance. Six typical urban surface materials were researched in this case study. The results showed that the transmittance was changed under different weather conditions and different urban surface materials had different infrared energy penetration of the atmospheric infrared window, which indicated different urban surface materials may have potentially different effects on the urban thermal environment. The results also indicated that the transmittance for different materials was affected not only by atmospheric transmittance but also by the distribution of emitted infrared energy along wavelengths, which provides a new perspective for related researchers to understand the phenomenon.