Thepolymerization　of　pyrrole　was　fabricated　on　gold　electrode　by　cyclic　scan　in　the　solution　of　0.1　mol/L　pyrrole　containing　0.　I　mol/L　KCl　between　-0.3　and　0.8　V　at　a　scan　rate　of　50　mV/s　for　10　cycles.　Then,　the　PPy　membrane　was　electrochemical　oxidated　of　at　+1.　2　V.　The　film　is　porosity.　Following,　the　double-stranded　calf　thymus　DNA　was　deposited　within　the　pores.　DNA　damage　induced　by　organic　pollutant　PFOS　was　studied　by　the　differential　pulse　voltammetry　(DPV)　and　take　methylene　blue　(MB)　as　electrochemical　indicator.　The　results　show　MB　reduction　peak　current　decreases　with　the　incubation　time　increasing　and　the　ionic　strength　enhanced.　It　indicates　that　the　interaction　of　PFOS　and　the　DNA　hinders　the　combination　of　guanine　(G)　and　MB.　The　electronic　transfer　resistance　has　increased　from　650　Omega　to　1350　Q.　It　indicated　DNA　damage　due　to　PFOS　reduces　the　electron　transfer　properties.　The　DNA　biosensor　provides　a　novel　avenue　to　research　the　pollutant　toxicology.