The invention discloses an emergency jettisoning system based on ultrasonic waves and unmanned aerial vehicle technology and relates to the field of emergency rescue of unmanned aerial vehicles. The emergency jettisoning system based on the ultrasonic waves and the unmanned aerial vehicle technology comprises a ground command center and an unmanned aerial vehicle body which comprises a flight control module, a GPS positioning module, a jettisoning control module, a resonant frequency detecting module, an ultrasonic emitting device, an image acquiring device, a calculating module and a wireless transmission module; the GPS positioning module, the jettisoning control module, the resonant frequency detecting module, the ultrasonic emitting device, the image acquiring device, the calculating module and the wireless transmission module are all electrically connected with the flight control module; the GPS positioning module is electrically connected with the jettisoning control module; and the resonant frequency detecting module is electrically connected with the ultrasonic emitting device. By means of the technical scheme, the fire fighting rescuing efficiency is improved, accuracy is high, the high rise operation risk can be lowered, and the safety of workers is guaranteed.