The invention discloses an ultrasonic 
distance detection-based unmanned aerial vehicle 
obstacle avoidance system and a control method thereof. The unmanned aerial vehicle 
obstacle avoidance system includes a flight control module, an airborne 
radio frequency communication module, an ultrasonic 
ranging module and an autonomous 
obstacle avoidance module, wherein the flight control module is used for controlling the flight of an unmanned aerial vehicle and feeding back the flight condition of the unmanned aerial vehicle to a 
ground station, the ultrasonic 
ranging module is used for detecting whether obstacles exist before, above and below the unmanned aerial vehicle as well as at the left and the right of the unmanned aerial vehicle, and detecting the distances between the unmanned aerial vehicle and the obstacles, and the autonomous obstacle avoidance module is used for controlling the unmanned aerial vehicle to perform obstacle avoidance according to measurement results of the ultrasonic 
ranging module. With the control method of the unmanned aerial vehicle obstacle avoidance 
system adopted, the unmanned aerial vehicle can autonomously avoid the obstacles, and the avoidance 
modes of the unmanned aerial vehicle can be more diverse, and the unmanned aerial vehicle can automatically adjust flight routes and accomplish specified flight tasks. The ultrasonic 
distance detection-based unmanned aerial vehicle obstacle avoidance system of the invention has the advantages of simple structure, convenient use and high practical value.