A system and method of using a drone to detect toxic and harmful gases. The detection system comprises a flight control system connected to a drone, and a data acquisition module, a wireless transmission module and an ultrasonic module separately connected to a microprocessor, and further comprises a geographic information module, a gas detection module and a ground center. The gas detection module and the geographic information module are both connected to the data acquisition module, and gas data and geographic data are transmitted to the ground center by means of the wireless transmission module. The ground center displays gas concentrations, and locates a pollution source on the basis of changes in gas concentrations at different locations. The detection system and the detection method can detect toxic and harmful gases and locate a pollution source in a polluted area inaccessible to humans, solving the problem in which it is difficult for an existing environmental emergency monitoring system to access co
