The　microstructures　and　tensile　properties　of　three　high　carbon　Fe-Ni-Mn-Si-C　steels　were　investigated　by　optical　microscope,　X-ray　diffraction　and　TEM.　The　results　show　that　twinning　induced　plasticity　effect　is　the　main　plasticity　mechanism　of　the　Fe-Ni-Mn-Si-C　steels.　With　the　increasing　of　carbon　content,　yield　strength　increases　from　391　MPa　to　458　MPa,　tensile　strength　increases　from　860　MPa　to　974　MPa,　and　elongation　increases　from　63.6%　to　69.2%.　The　dynamic　strain　aging　becomes　more　obvious　with　the　increasing　of　the　carbon　content.　Fe-15Ni-12Mn-2.5Si-XC　steels　have　high　strain　hardening　capacity,　and　the　maximal　strain　hardening　exponent　of　the　steels　can　reach　up　to　0.73　when　the　carbon　content　increases　to　0.98%.