In order to discover the forest fire at the early stage, the video based fire smoke detection system should be developed. This paper proposes an improved ViBe algorithm to overcome the drawbacks of ViBe which is widely used in forest fire smoke recognition. To make the algorithm faster, the improved ViBe algorithm introduces a switch variable to control the model updating every 2 frames. Also, the new ViBe algorithm contains a method to detect if the scene is changing, and upon finding the changing, a fast updating strategy would be used to increase the adaptive ability. The experiments are done from 2 aspects, to test the time consuming and adaptive ability of the improved algorithm. The experiments results show that the improved ViBe algorithm has better performance compared to ViBe algorithm and GMM algorithm, and can detect the forest fire smoke accurately in different conditions.