1. In an image processing software including a trigger parameter and a stop parameter, a method for setting an image monitoring area, comprising the steps of: (a) running the image processing software to calculate and analyze a plurality of continuous image frames taken in a predetermined space by an image fetching unit; (b) determining whether the trigger parameter is included in a target image in one of the image frames; (c) responsive to the determination in step (b) being affirmative, automatically calculating, analyzing, and recording a trace of the target image moving in the image frames; (d) determining whether the stop parameter is included in the target image in the other image frames; and (e) responsive to the determination in step (d) being affirmative, stopping the recording of the trace of the target image and setting an area defined by the trace of the target image as an image monitoring area to be monitored.