Abstract: In order to meet the real-time requirement of the video sequence fusion in visible and infrared target tracking, region growing method, a frequently used method in target segmentation during target tracking; was used to extract the target regions from IR image through the gray difference between IR targets and its backgrounds. The extracted target regions of IR image are fused with background regions of visible image. The fused mosaic image has good IR target features as well as clear visible background. Experiment shows that the method is simple and effective.