Saving　power　and　extending　identification　distance　are　important　problems　in　portables.　This　paper　presents　a　system　on　chip　for　radio　frequency　identification　(RFID)　active　tag　to　extend　the　identification　distance　and　battery　life.　It　uses　hardware　and　software　to　execute　the　checking,　identifying　and　real　time　anti-collision.　RE　module　and　active　tag　system　have　been　completed.　Methods　for　low　power　consumption　and　a　simple　practical　adjusting　approach　for　RE　module　are　introduced.　The　proposed　system　has　advantages　such　as　simple　structure,　low　cost,　and　low　energy　electron　diffraction.　This　system　is　successfully　used　in　433/868/915　MHz　RFID.　When　TX　power　is　adjusted　by　the　software,　the　identification　distance　is　between　80meters　and　120meters.