1. A method for displaying a stereoscopic image, the stereoscopic image comprising a first-eye image and a second-eye image, the method comprising steps of: (a) dividing the first-eye image into a plurality of first search frames, the first search frames comprising N effective search frames, N being a natural number; (b) searching for a target frame in the second-eye image according to each of the effective search frames in the first-eye image; (c) calculating a parallax according to the position of each of the effective search frames in the first-eye image and the position of the corresponding target frame in the second-eye image; (d) calculating a shift of the first-eye image with respect to the second-eye image according to the parallaxes; (e) moving the first-eye image for a length of the shift; and (f) outputting the moved first-eye image and the second-eye image to display the stereoscopic image; wherein before the step (a), the method further comprises performing a high-pass filtering to the first-eye image and the second-eye image; the step (b) further comprises (b1) searching for the corresponding target frame in the second-eye image according to an ith effective search frame, i being an integer ranging from 1 to N; the step (c) further comprises: (c1) judging whether the target frame is effective, if YES, calculating a the corresponding parallax according to the position of the ith effective search frame in the first-eye image and the position of the corresponding target frame in the second-eye image; and (c2) performing the steps (b1) and (c1) to each of the N effective search frames to obtain M parallaxes, M being an integer ranging from 1 to N; and the step (d) further comprises (d1) calculating the shift according to the M parallaxes.