There is a need to downscale the video (from image size M x N to M/2 x N/2) prior to transmission due to bandwidth limitation on the cannel. The conventional method for downscaling the video sequence is to decompress the video bitstream and then reencode it again at video server. This process is computationally intensive because of the motion estimation required during the reencoding process. In this paper, we proposed a polynomial motion-vector resampling (PMVR) algorithm to compute motion vectors for the downscaled video sequence in compressed domain. The proposed approach leads to significant computational saving compared with the conventional spatial domain approach. Simulation results suggest that the proposed method is effective for video downscaling.