A low complex H.263 to H.264 P-frame transcoder is presented in this paper. The new scheme uses an early-stop skip-mode process, a motion vector refinement algorithm and a simplified inter-mode decision module. Experiment results show that the proposed transcoding scheme can achieve a remarkable reduction of computational complexity at the cost of a negligible rate-distortion loss (under 0.6 dB) as compared with the full transcoder.