Abstract: A method of downscale decoding MPEG-2 video includes an Inverse Discrete Cosine Transformation (DCT) procedure for performing a ½ horizontal downscaling to convert DCT coefficients in a 8×8 array block of the video into a 4×8 array intra-block and performing a ½ vertical downscaling to convert the intra-block into an intra-coded picture having ¼ resolution of the original; and a downscaling motion compensation procedure for performing a motion compensation to the current intra-block to obtain a predictive block having ½ horizontal size of the original, adding the predictive block with a residual block produced by the same method applied to the intra-blocks to obtain a 4×8 array inter-block, and performing a ½ vertical downscaling to the inter-block for outputting a predictive-coded picture and a bidirectional predictive-coded picture having ¼ resolution of the original, so as to simplify the complexity of the decoding computation and enhance the decoding speed.