The　effects　of　high　carbon　content　on　the　microstructure　and　tensile　properties　of　Fe-20Mn-3Cu-xC　TWIP　steels　were　studied　by　OM,　XRD,　SEM　analysis.　The　experimental　results　indicate　that　the　amount　of　carbide　and　micro-porosity　increased　with　the　increasing　of　carbon　content.　The　microstructures　in　the　undeformed　and　deformed　region　of　Fe-20Mn-3Cu-xC　steels　exhibit　fully　austenitic　phase.　The　fractography　of　tensile　samples　reveals　typical　tough　fracture　microstructure　with　isometric　dimples.　The　number　of　carbide　in　the　as-cast　structure,　the　yield　strength　and　the　tensile　strength　increase　with　the　increasing　of　carbon　addition,　but　the　elongation　rate　increases　at　first　and　then　decreases.　TWIP　steel　has　the　optimum　property　when　the　carbon　addition　is　1.3　mass　pct,　of　which　the　tensile　strength　is　1040.59　MPa,　the　elongation　percentage　is　98.08%　and　the　strength-elongation　product　achieves　102061.07MPa.%.　Fe-20Mn-3Cu-xC　steels　have　high　strain　hardening　capacity,　and　strain　hardening　rate　(theta)　and　strain　hardening　index　(n)　both　increase　with　the　increasing　of　C　addition.