A　novel　DNA　biosensor,　which　combines　the　merits　of　micro-fluidic　chips,　the　electrophoretic　driving　mode,　paramagnetic　beads　amplification,　and　laser-induced　fluorescence　detection　was　developed　for　the　rapid　and　sequence-specific　detection　of　DNA　in　this　study.　The　proposed　DNA　biosensor　has　much　higher　discrimination　ability　for　the　detection　of　single-base　mismatch　and　much　stronger　resistibility　to　the　complex　matrixes　of　real　samples　in　comparison　with　previous　biosensors.　These　features,　as　well　as　its　ease　of　fabrication　(the　fabrication　of　the　sensor　takes　only　10　min　except　the　fabrication　of　micro-fluidic　chip),　operation　convenience,　stability,　better　re-usability　(micro-fluidic　chip　can　be　reused　without　any　extra　treatment)　and　short　analysis　time　(one　determination　only　takes　15　min),　make　it　a　promising　alternative　to　rapid　detection　of　DNA　in　clinical　diagnosis.　With　the　help　of　the　biosensor,　we　successfully　determined　DNA,　which　related　to　oral　cancer,　in　a　saliva　sample　without　any　pre-separation　or　dilution　with　a　detection　limit　of　4.2　x　10(-11)　M　and　a　relative　standard　deviation　(n　=　5)　＜　5　%.　The　success　in　the　present　biosensor　served　as　a　significant　step　toward　the　practical　application　of　the　biosensor　in　clinical　diagnosis.