Aimed　at　higher　computational　complexity　of　H.264/AVC　due　to　searching　all　inter-fame　modes　based　on　rate-distortion　optimization　(RDO),　a　fast　and　optimized　encoding　algorithm　was　proposed.　Analyzed　the　statistical　probability　characteristics　of　different　modes　appeared　in　inter-frame,　the　predictions　for　special　inter-frame　modes　were　carried　out　to　stop　unnecessary　searching　and　computing　RDO　and　reduce　the　encoding　time.　The　simulation　results　show　that　the　proposed　algorithm　can　reduce　total　encoding　time　about　70%　averagely,　holding　almost　the　same　PSNR,　bit-rate　and　output　stream　structure,　compared　with　the　standard　H.264　scheme.