Abstract: In this study, direct sequence ultra-wideband (DS-UWB) technology is applied to Unmanned Aerial Vehicle (UAV) communication link design. DS-UWB technology is loosely defined as the signal occupies a bandwidth of more than 25% of a center frequency, or more than 1.5 GHz and it is modulated by direct sequence. The problem of the selection of monocycle which is suitable for UWB communication system of UAV is discussed. In the case of limited payload, the mathematical model of propagation characteristics of DS-UWB UAV communications is analyzed and established in free space and frequency dependent two-ray path channel. In two-ray path model, rake receiver is employed, which uses maximum ratio combing technology. The model reveals the relations among the propagation parameters, such as the Bit Error Rate (BER), transmission distance and data transmission rates, different orders of Gaussian pulse and transmission power. Simulation results show that: in the same situation of the BER, transmission distance and data transmission rate, the first order Gaussian pulse has the minimum transmission power. Due to UAV’s limit of payload, the first order DS-UWB should be employed as the carrier waveform. In the situation of BER equals to 10-6, the SNR of two-ray path model is 3.01 dB lower than free space model. The transmission power of the two-ray path model is about 50% lower than free space propagation model and the BER performance of two-ray model is better than free space model. All of those provide a basis for the signal chosen of DS-UWB UAV communication links.