With　the　rapid　development　of　microprocessor,　embedded　multimedia　products　are　gradually　becoming　the　mainstream　in　the　market.　However,　the　high　coding　efficiency　enabled　by　the　H.264　video　compression　standard　comes　with　substantially　greater　algorithmic　complexity　as　compared　to　that　of　existing　standards.　And　this　additional　complexity　results　in　many　difficulties　in　the　implementation　and　optimization　tasks.　This　paper　firstly　analyses　the　block　size　prediction　algorithms　of　Intra　&　Inter　frame,　and　then　improves　it　through　autocorrelation　and　combining　sum　of　absolute　difference　(SAD)　and　analysis　of　texture　difference　respectively.　The　experimental　results　indicated　that　the　new　algorithms　achieved　significant　improvement　as　compared　to　the　original　encoder.　Finally,　some　optimization　techniques　about　H.264　on　TMS320DM642　DSP　platform,　which　can　effectively　enhance　the　video　coding　speed,　are　proposed.　©　2007　IEEE.