In　this　paper,　we　design　a　temperature　sensing　system　based　on　a　DSP　chip　TMS320F2812　for　a　real-time　PCR　instrument.　In　this　system,　we　design　a　4-wire　temperature　sensing　module　with　a　thermal　resistor　PT　100　to　measure　the　temperature　and　convert　it　into　a　voltage　signal.　Then　the　voltage　signal　is　digitalized　by　the　ADC　module.　At　last,　the　data　are　transferred　to　a　PC　through　the　serial　port.　The　experimental　results　show　that　the　linearity　of　the　system　is　0.99　with　the　standard　deviation　of　0.0419.