H.264/AVC　is　the　newest　video　coding　standard　with　high　compression　efficiency.　Because　it　will　take　a　long　time　to　code　with　extremely　complex　algorithm,　it　can　not　achieve　real-time　application.　In　this　paper,　according　to　the　feature　of　intra-frame　prediction　algorithm,　a　fast　algorithm　based　on　characteristic　of　4×4　sub-block　is　proposed.　This　algorithm　makes　use　of　the　real　condition,　then　selects　one　from　the　nine　prediction　directions.　Therefore,　it　can　reduce　complexity　of　algorithm　and　coding　time　dramatically.　Experimental　results　show　that　the　compression　time　of　proposed　algorithm　is　18.98%　less　than　that　of　H.264/AVC,　at　the　expense　of　a　little　quality　degradation.　©　2007　IEEE.