1. A method for marking electronic document, comprising: performing a correction procedure before an eye tracking procedure is executed, wherein the correction procedure includes sequentially receiving a plurality of correction images, and generating a coordinate transformation matrix according to the correction images; displaying an electronic document in a display unit; capturing an image sequence of a user by an image capturing unit; executing the eye tracking procedure, a nod detecting procedure and a blink detecting procedure to analyze the image sequence, wherein the eye tracking procedure is configured to track a movement trajectory of eyes of the user, and the nod detecting procedure and the blink detecting procedure are configured to detect whether the user performs a first specific action or a second specific action; wherein the eye tracking procedure includes: detecting an eye area of a current image in the image sequence to obtain a pupil position in the current image; obtaining a comparison correction parameter according to two bright spot positions of the eye area of the current image; obtaining a dynamic compensation parameter according to a reference correction parameter and the comparison correction parameter, wherein the reference correction parameter is obtained based on the two bright spot positions of the eye area in each of the correction images; calculating eye movement coordinates according to the pupil position in the current image, the dynamic compensation parameter and one of the two bright spot positions of the current image; transforming the eye movement coordinates into sightline falling coordinates corresponding to the display unit by using the coordinate transformation matrix; and recording the sightline falling coordinates; obtaining a first position on the electronic document where a current sightline of the user falls through the eye tracking procedure when detecting the user performs the first specific action; executing a marking action for marking the electronic document along with the movement trajectory of the user's eyes starting from the first position; obtaining a second position on the electronic document where the current sightline of the user falls through the eye tracking procedure when detecting the user performs the second specific action; and finishing the marking action at the second position.