Herein,　a　signal　magnification　electrochemical　aptasensor　for　the　detection　of　breast　cancer　cell　via　free-running　DNA　walker　is　constructed.　Theoretically,　just　one　DNA　walker,　released　by　target　cell-responsive　reaction,　can　automatically　cleave　all　D-RNA　(a　chimeric　DNA/RNA　oligonucleotide　with　a　cleavage　point　rArU)　anchored　on　electrode　into　shorter　produces,　giving　rise　to　considerably　detectable　signal　finally.　Under　the　optimal　conditions,　the　electrochemical　signal　decreased　linearly　with　the　concentration　of　MCF-7　cell.　The　linear　range　is　from　0　to　500　cells　mL-1　with　a　detection　limit　of　47　cells　mL-1.　In　a　word,　this　approach　may　have　advantages　over　traditional　reported　DNA　machines　for　bioassay,　particularly　in　terms　of　ease　of　operation,　cost　efficiency,　free　of　labeling　and　of　complex　track　design,　which　may　hold　great　potential　for　wide　application.　©　2016　Elsevier　B.V..