An　improved　dynamic　framed　slotted　Aloha　algorithm　(IDFSA)　based　on　the　radio　frequency　identification　system　is　presented.　IDFSA　divides　the　tags　into　different　frequency　channels　in　the　design　period　and　saves　the　communication　time.　In　the　meantime,　IDFSA　optimizes　the　real-time　slots　accounts　obtained　after　frequency　division,　reducing　the　colliding　efficiency　up　to　2.67　times,　and　improves　the　system　efficiency.　IDFSA　dissolves　the　problem　that　the　slots　amount　increases　exponentially　with　an　increasing　of　the　identified　tags　amount.　IDFSA　has　been　used　in　the　433/868/915　MHz　system,　verifying　this　method　easy　and　efficiency.