The　influence　of　carbon　content　on　the　stacking　fault　energy　(SFE)　of　Fe-20Mn-3Cu　twinning-induced　plasticity　(TWIP)　steel　was　investigated　by　means　of　X-ray　diffraction　peak-shift　method　and　thermodynamic　modeling.　The　experimental　result　indicated　that　the　stacking　fault　probability　decreases　with　increasing　carbon　addition,　the　SFE　increases　linearly　when　the　carbon　content　in　mass　percent　is　between　0.　23%　and　1.　41%.　The　thermodynamic　calculation　results　showed　that　the　SEE　varied　from　22.　40　to　29.　64　mJ　.　m(-2)　when　the　carbon　content　in　mass　percent　change＇s　from　0.　23%　to　1.　41%.　The　XRD　analysis　revealed　that　all　steel　a　were　fully　austenitic　before　and　after　deformation,　which　suggested　that　TWIP　effect　is　the　predominant　mechanism　during　the　tensile　deformation　process　of　Fe-20Mn-3Cu-XC　steels.