A video indexing method includes: analyzing trajectory information of a plurality of objects in video data and storing a plurality of pieces of object trajectory data obtained correspondingly in a storage device; determining whether the storage device satisfies a data removal condition; when the data removal condition is satisfied, performing an object trajectory analysis on the plurality of pieces of object trajectory data to select at least one target object from the objects; and extracting the object trajectory data of the at least one target object from the storage device and generating at least one video indexing image accordingly.