In order to improve the speed and quality of video mosaic, Fast Mosaic of Unmanned Aerial Vehicle Video based on Improvement Model Fitting (FMUAVRVIMF) was proposed. Firstly, Fast Adaptive Robust Invariant Scalable Feature Detector (FARISFD) was used for video frames registration. Then, the improved Random Sample Consensus(RANSAC) algorithm was proposed for model fitting, and false matching points were removed. Finally, Fast Mosaic of Reconnaissance Frames algorithm was proposed to calculate homography matrix which transformed frames to orthophoto mosaic image, the video sequence mosaic was compeleted. The experiment results show that Improved Random Sample Consensus ensures the robustness, and the mosaic speed was increased, and the mosaic effect was improved.