A high accuracy image mosaicking method based on big virtual camera is proposed for multi-camera system on the optical remote sensing satellite to realize the high-precision stitching of multi-camera images. A big virtual camera is built according to the geometric imaging model of each single camera, and the geometric correction is performed by coordinate forward and back calculation based on their imaging models to obtain each single virtual image in the virtual camera image coordinate system. The final stitched image can be obtained by stitching single virtual image based on its coordinate information. By using the concept of big virtual camera, the high accuracy stitched image and corresponding rational function model for post processing are obtained at the same time. It can be used for multi-camera system with different quantities and resolutions to realize automatic intelligent ground preprocessing.