The　microstructure　and　mechanical　properties　of　three　kinds　of　low-carbon　medium-manganese　steels　with　different　Si　contents　under　an　intercritical　heat　treatment　process　were　studied.　The　results　show　that　the　microstructure　of　the　test　forged　steel　is　mainly　composed　of　ferrite　and　pearlite.　After　900　degrees　C　complete　austenitizing　quenching　+　720　degrees　C　intercritical　quenching,　the　microstructure　of　the　test　steel　is　mainly　composed　of　ferrite　and　martensite.　With　the　increase　in　Si　content,　the　microstructure　becomes　finer　and　more　uniform.　The　microstructure　of　the　test　steel　after　900　degrees　C　complete　austenitizing　quenching　+　720　degrees　C　intercritical　quenching　+　680　degrees　C　intercritical　tempering　is　dominated　by　ferrite　and　tempered　martensite,　with　a　small　amount　of　retained　austenite　and　cementite.　As　the　Si　content　increases,　the　boundaries　between　ferrite　and　tempered　martensite　become　more　clear.　The　tensile　strength　and　hardness　of　the　test　steel　increase　with　the　increase　in　Si　content,　while　the　elongation　first　increases　and　then　decreases;　the　comprehensive　performance　of　the　test　steel　is　the　best　when　the　Si　content　is　0.685　wt.　%,　with　a　tensile　strength　of　726　MPa,　a　yield　ratio　of　only　0.65,　the　highest　elongation　of　30.5%,　and　the　highest　strong　plastic　product　of　22,143　MPa.%.