The invention provides an air pollution monitoring system and an air pollution monitoring method based in an unmanned aerial vehicle. The system comprises an unmanned aerial vehicle body and a ground station. The unmanned aerial vehicle body is provided with a data collection control unit, wherein an input end of the data collection control unit is respectively connected with a gas detection module, a GPS navigation module, a temperature and humidity sensor and an onboard power supply; an output end of the data collection control unit is respectively connected with an onboard image transfer radio, an SD storage card and a data export interface; and the data collection control unit respectively transmits data with a CCD optical camera and an onboard data transfer radio in a bidirectional manner. The ground station is provided with an industrial personal computer, wherein the industrial personal computer respectively transmits data with the data transfer radio, a display and a storage unit in a bidirectional manner, an input end of the industrial personal computer is connected with the image transfer radio, and the power supply powers the industrial personal computer, the image transfer radio and the data transfer radio. The air pollution monitoring system adopts the unmanned aerial vehicle to implement field monitoring, so that detection staffs can be far away from pollution, monitoring efficiency can be improved, and accuracy and rapidness of monitoring data can be ensured.