One　of　the　largest　disadvantages　in　radio　frequency　identification　(RFID)　system　is　its　low　tag　identification　efficiency　by　tag　collision.　When　the　number　of　tags　is　large,　for　the　conventional　RFID　anti-collision　algorithm　the　number　of　slots　required　to　read　the　togs　increases　exponentially　as　the　number　of　tags　does.　The　proposed　IDFSA　algorithm　solved　this　problem　by　dividing　frequency　of　tags　that　is　grouping　the　togs　in　different　frequency　channel,　reducing　the　number　of　slots　and　saving　the　communication　time　Of　grouping　with　estimation.　The　reader　requests　every　frequency　in　turn　to　check　the　tags.　In　every　frequency　channel,　the　optimal　frame　size　was　set　to　enhance　the　system　efficiency.　This　Algorithm　has　been　used　in　the　433/868/915　RFID　system.　The　system　identification　efficiency　shows　good　performance.