Abstract: In this paper, the drill pipe bore is considered as an ultra long irregular lossy circular waveguide, and the channel model is established by using multipath transmission theory. Meanwhile, the channel characteristics and signal attenuation mechanism are analyzed, combining the experimental statistics. The analysis results show that the API 5″ and 5^1/2″ drill pipe bore, widely applied in air drilling field, can be used as the 2.4 GHz band microwave channel, and are in accordance with the ultra wide band (UWB) channel standard. However, the numerous reflected waves are generated by the reflective surface in the joint section of the drill pipe, which makes the channel has the characteristics of dual cluster and multi-path channel. The large delay between the two clusters leads to a significant increase of the root mean square delay spread, and according to the model contrast results, the multipath fading and delay are the main factors affecting the propagation quality.