In　order　to　control　the　high　complexity　of　H.264　encoder,　a　novel　complexity　allocation　and　control　(CAC)　algorithm　for　H.264　inter　coding　is　proposed　in　this　paper,　based　on　the　reorder　of　candidate　inter　modes　with　priorities　and　the　new　complexity-rate-distortion(C-R-D)　cost　functions.　This　algorithm　can　be　performed　both　at　the　frame　level　and　the　macroblock　(MB)　level,　so　as　to　achieve　a　more　efficient　complexity　control.　Experimental　results　show　that　our　proposed　algorithm　can　adaptively　control　the　complexity　of　inter　coding　at　any　appropriate　levels　according　to　the　current　energy　condition　of　a　mobile　device　while　maximizing　the　video　quality,　so　as　to　prolong　the　operational　lifetime　of　batteries.