An unmanned flying spray system includes a flying device, an air valve, and a spraying device. The flying device is provided with a controller including a control module and a power supply module electrically connected to the control module for supplying power to the flying device. The air valve is disposed on the flying device and connected with a gas cylinder for outputting a gas power. The spraying device includes a pesticide container, an electromagnetic control valve electrically connected with the control module, and a nozzle. The pesticide container has a diverting member connected with the air valve, the pesticide container, and the nozzle. The electromagnetic valve is disposed between the diverting member and the nozzle. The unmanned flying spray system sprays a liquid by use of gas power, so as to significantly reduce the overall weight and improve the stability of flying.
