In　this　paper,　a　content-based　encryption　scheme　for　wireless　H.264　video　in　the　compressed　domain　is　proposed.　First,　the　information　of　prediction　mode,　motion　vector　and　prediction　residual　energy　is　extracted　from　H.264　bitstream　and　then　jointly　utilized　to　compute　measures　to　classify　the　complexity　of　the　video　content　in　terms　of　texture　and　motion.　Then　according　to　the　classification　results,　videos　with　different　content　features　are　encrypted　with　selective　encryption　in　different　ways　in　the　unit　of　GOP　(GOP,　Group　of　Pictures).　In　the　case　of　videos　of　complex　texture,　we　encrypt　all　the　intra　prediction　modes　and　DCT　coefficients　in　the　GOP;　as　for　videos　of　not　that　much　texture,　the　number　of　high-band　coefficients　to　encrypt　will　be　reduced.　As　for　videos　of　high　motion　intensity,　we　encrypt　MVDs　in　all　the　P　frames　in　the　GOP;　while　as　for　those　of　medium　or　low　intensity,　only　MVDs　in　parts　of　P　frames　in　the　GOP　are　to　encrypt.　Experiments　have　shown　that　compared　to　the　existing　algorithm　of　SEH264,　the　proposed　content-based　video　encryption　scheme　can　provide　good　performance　in　both　aspects　of　security　as　well　as　computational　complexity.　Moreover,　the　proposed　encryption　scheme　is　implemented　entirely　in　the　compressed　domain　and　format-compliant　with　the　H.264　bitstream　without　influence　on　the　compression　ratio.　©　2012　IEEE.