At present, in order to get a large field of view image, image mosaic technique has been widely applied in UAV remote sensing platform. The traditional mosaic system for UAV remote sensing image takes a lot of time and man power, it is difficult to complete the image stitching automatically. In the paper, an approach for geometric correction of remote sensing image without any ground control points is presented, and the SIFT algorithm is used to extract and match feature points. Finally, the weighted average fusion method is used to smooth the image after splicing and an automatic mosaic system for UAV remote sensing video images is developed. In order to verify the system, some splicing ex-periments using UAV actual aerial photography images have been done and good results have been achieved.