The invention discloses a GNSS high-precision assisted unmanned aerial vehicle three-dimensional measurement method, which uses an airborne GNSS receiver, a GNSS base station receiver, and a camera for synchronous observation, including: the airborne GNSS receiver accurately records the exposure time of the camera, and uses a carrier After the phase difference is decomposed and calculated, the centimeter-level position information of the antenna is obtained, and then the outer bearing line element at the exposure time of the camera is obtained by interpolation, which is used as the starting data. Combined with a small number of ground control points, the aerial triangulation software is used for automatic processing, and each image is obtained. The outer orientation elements of the film, and then produce the required 4D image. The present invention adopts the method of differential positioning, and uses the GNSS differential position information corrected by the eccentricity to replace the position information of the exposure point, so as to obtain the line elements in the outer orientation elements required in aerial photogrammetry, which greatly improves the accuracy of the UAV. The efficiency of low-altitude photogrammetry reduces field workload.