The invention relates to a measuring method, system and device based on oblique photography, and a storage medium. The method comprises the following steps of controlling an unmanned aerial vehicle tofly according to a set flying trajectory, collecting image information of a target object in a to-be-measured area by photography, performing aerotriangulation according to the image information of the target object, and building a spatial three-dimensional model; selecting a plurality of surface points of the spatial three-dimensional model according to a preset point location selection rule, and establishing a main baseline and an auxiliary baseline of the target object according to the surface points; and determining position information of the target object according to the main baselineand the auxiliary baseline. The measuring method is accurate in collecting result and relatively high in efficiency; most of field operations are transferred into a room and subjected to computer-aided processing, so that the field operation risk of an operator is eliminated, the operation cost is reduced, and the problem of difficult field collection due to the closure and privacy of the target object is solved; and the measuring method is suitable for popularization and use of large-scale high-precision measurement.