A　novel　microfluidic　chip-based　fluorescent　DNA　biosensor,　which　utilized　the　electrophoretic　driving　mode　and　magnetic　beads-based　sandwich　hybridization　strategy,　was　developed　for　the　sensitive　and　ultra-specific　detection　of　single-base　mismatch　DNA　in　this　study.　In　comparison　with　previous　biosensors,　the　proposed　DNA　biosensor　has　much　more　robust　resistibility　to　the　complex　matrix　of　real　saliva　and　serum　samples,　shorter　analysis　time,　and　much　higher　discrimination　ability　for　the　detection　of　single-base　mismatch.　SNPs　genotyping/detection　in　clinical　diagnosis.　By　using　the　biosensor,　we　have　successfully　determined　oral　cancer-related　DNA　in　saliva　and　serum　samples　without　sample　labeling　and　any　preseparation　or　dilution　with　a　detection　limit　of　5.6　x　10(-11)　M,　a　RSD　(n　=　5)　＜　5%　and　a　discrimination　factor　of　3.58-4.54　for　one-base　mismatch.