Methods and apparatuses for encoding and decoding video are provided. The encoding method includes: performing motion estimation on a current block according to a first sub-pixel unit, and obtaining a motion vector in the first sub-pixel unit with respect to the current block; interpolating a reference picture indicated by the motion vector according to a second sub-pixel unit smaller than the first sub-pixel unit; using the interpolated reference picture, selecting a second sub-pixel in the second sub-pixel unit adjacent to a first sub-pixel in the first sub-pixel unit of the reference picture; selecting a corresponding region that has a smaller error with the current block, from among a first corresponding region of the reference picture and obtained with respect to the first sub-pixel, and a second corresponding region of the current block and obtained with respect to the selected second sub-pixel; and encoding information of the selected corresponding region.