A video encoding method for a video encoding device is provided. The method includes: obtaining a current image and a reference image, wherein the current image has a first block; obtaining motion vectors, wherein each of the motion vectors points to a reference block in the reference image; for each of the motion vectors, executing a filter calculation according to the pointed reference block and the first block to generate a first filter block, and calculating an difference value according to the pointed reference block and the corresponding first filter block. The method also includes: obtaining a minimum first difference value among the difference values, and obtaining a second filter block corresponding to the first difference value; encoding the first block according to the second filter block. Accordingly, the video quality and the compression ratio are increased.