In order to explore the stitching accuracy and efficiency of regional scale unmanned aerial vehicle (UAV)forest images, SIFT algorithm, SURF algorithm, ORB algorithm and KAZE algorithm were used to study of the UAV images stitching for different canopy density forest stand. Firstly, four algorithms were used to extract feature points from UAV images, match feature points and fuse the images with gray weighted fusion, so that multiple UAV images could be assembled into one image. Then, image feature extraction, feature matching, matching accuracy and image stitching consumption under different canopy density were compared and analyzed. The results showed that : for the two images stitching, the number of feature points extracted from low canopy density stand images was lower than that in high canopy density stand images. The feature matching rate of ORB algorithm was significantly lower than other algorithms, but the time consumed was the shortest, so if the accuracy is not high, the ORB algorithm can be used to quickly stitching images ; for medium find high canopy density stand images stitching, the correct matching ratio of SIFT algorithm and SURF algorithm was about 45% , and KAZE algorithm was about 55%. Therefore, if the image stitching requires higher precision, the KAZE algorithm is suitable; from the average time of stitching 64 images and the correct matching rate of the average feature points, since the stitching images was mostly medium and high canopy density stand, the correct matching rate of the average feature points of SIFT algorithm, SURF algorithm and KAZE algorithm was better, but the time spent by SURF algorithm image mosaic was 577. 8 s, which was significantly lower than 876. 3 s of SIFT algorithm and 806.8s of KAZE algorithm; from the aspect of visual effect, SIFT algorithm, SURF algorithm and KAZE algorithm have better visual effects, while the ORB algorithm has obvious dislocation and deformation phenomena. The results of this paper can provide some reference for the selection of UAV image stitching algorithms with different stands and different canopy density. [ABSTRACT FROM AUTHOR]