Abstract: With the development of various aircrafts and integrated communications integration, the research on the characteristics of air-ground channels becomes more and more important and urgent. For the air-ground communication scenario, an unmanned aerial vehicle (UAV) air-ground channel measurement system composed of a UAV transmitting unit and a ground receiving unit is developed in this paper. In this system, ZC sequence with flat power spectrum and large dynamic range is chose as the measurement sequence, the channel impulse response (CIR) is extracted in real-time on the hardware platform, and the sampling deviation recovery and system response correction are developed to improve the accuracy of the measurement system. The verification results show that the measured results of developed channel measurement system are well consistent with the preset channel of channel emulator and the ray tracing (RT) simulation results. Finally, the field measurements are carried out in the campus scenario, and the channel characteristics, i.e., path loss (PL), Rice K-factor, root mean square-delay spread (RMS-DS) are analyzed.