H.264/AVC　is　the　newest　video　coding　standard　with　high　compression　efficiency.　Because　it　will　take　a　long　time　to　code,　it　can　not　achieve　the　real-time　application.　An　efficient　algorithm　based　on　autocorrelation　is　proposed　in　this　paper.　This　algorithm　will　predict　every　macroblock　before　coding,　then　selecting　one　of　the　two　prediction　modes.　Therefore,　coding　time　can　be　reduced　dramatically.　Experimental　results　show　that　the　compression　time　of　proposed　algorithm　is　26.9%　less　than　that　of　H.264/AVC,　only　increases　a　little　bit,　and　the　SNR　is　invariable.