A motion estimation method for a succession of frames in a digital coding system includes: with reference to a first block in a first frame, searching a second frame for a second block that corresponds to the first block; and estimating a motion vector of the first block with respect to the second block in the second frame. Blocks in the second frame are searched according to a distance-weighted search sequence starting from a candidate origin block. In view of the radiating characteristics of motion vectors, the distance-weighted search sequence can save unnecessary search time.