To　reduce　the　encoding　time　for　H.264　and　apply　it　to　the　real-time　practice,　on　the　basis　of　the　research　on　the　block　size　prediction　of　intra　frame　and　according　to　the　histogram　algorithm,　an　intra　4×4　mode　or　intra　16×16　mode　for　every　macro-block　are　selected　before　coding.　If　the　intra　4×4　prediction　mode　is　chosen,　then　the　fast　algorithm　based　on　the　characteristic　of　macro-block　itself　is　used　to　reduce　the　choices　for　predicted　directions.　Experimental　results　show　that　without　the　variety　of　PSNR,　the　compression　time　is　32.8%　less　than　that　of　the　original　and　it　increases　3.2%　bits　rate.