Proposed is an efficient mode decision for H.264/AVC frame-skipping transcoding. In the proposed algorithm, all information including mode, motion vector etc. are reused when the selected best reference frame is not skipped; while an efficient mode decision is employed when the best reference frame is dropped. Experimental results reveal that an average of 70 of computation time can be saved compared to the fully decoding/encoding procedure. Degradation in the rate-distortion performance is fairly small.