As　some　research　results　show,　LED　lighting　has　an　obvious　luminous　flux　decrease　with　LED＇s　junction　temperature　increasing.　The　constant　power　control　strategy　is　suitable　to　achieve　constant　luminous　flux　when　junction　temperature　varies.　This　paper　puts　forward　a　kind　of　constant　power　control　strategy　based　on　multiplier　and　establishes　its　small-signal　model.　Considering　its　characteristics　of　low　cost　and　high　efficiency,　integrated　single-stage　PFC　circuit　is　widely　applied　in　the　medium　and　small　power　LED　drive　power　supply.　The　paper　adopts　Buck-Flyback　working　in　Transition　Mode(TM)　to　realize　constant　power　control　with　control　chip　L6562.　At　last,　the　simulation　and　experiment　were　set　up　to　verify　the　theoretical　analysis.