First, the autopilot of the unmanned aerial vehicle(UAV), based on the open source architecture, is designed and developed. Secondly, the small hexcopter UAV is built for the forest fire monitoring. The significant detection method is adopted to deal with the returned fire video, and the process such as the fire candidate region selection, feature fusion, feature classification, threshold judgment is employed to judge the occurrence of forest fires. If a fire occurs, the algorithm can compute the shape, area and spread speed and other information of the fire automatically, and start warning with the help of the photoelectric smoke sensor. The system has the characteristics of vertical takeoff and landing, low demand for weather, low use and maintenance costs.