The unmanned aerial vehicle (UAV) platform has broad prospects in a variety of forest fire monitoring and warning means, with characteristics of less operation cost, simple operation, flexibility and so on. Based on infrared detector for detection and warning of the fire point, a forest fire warning system was presented with low-cost rotor UAV as a platform, using the Beidou receiver module for UAV positioning. Theoretical calculation and practical examples were given to verify the practicability of this scheme. The results show that the system can locate the fire point quickly and accurately without personal real-time monitoring, which provides a solution for the prevention of forest fire and rapid fire fighting command.