In this paper we propose a method for detecting the presence of flame in a video stream in a natural environment. Firstly, the anomaly of image sequence is detected by background subtraction method. Then, the image sequence of the abnormal situation is segmented, and the area of the suspected flame is extracted. Finally, through the color and the shape feature recognition, to determine whether the segmentation region belongs to flame, if it belongs to the flame, it will send out a fire alarm.