Key-frame　extraction　technology　is　a　fundamental　process　in　content-based　video　retrieval.　Key　frame　provides　suitable　abstract　for　video　browse　and　retrieval　and　can　reduce　the　data　of　the　video　indexing　greatly.　At　first　the　existing　approaches　is　discussed　briefly,　then　a　new　method　for　key　frame　extraction　based　on　mutual　information　and　image　entropy　is　proposed.　Experimental　results　show　that　this　proposed　approach　is　able　to　extract　key　frames　adaptability　and　represent　video　content　more　effectively.　©　2011　IEEE.