In　the　present　study,　FeCoCrNiMnSix　(x　=　0,　0.1,　and　0.2,　molar　ratio)　high-entropy　alloys　(HEAs)　were　prepared　via　arc　melting,　and　subsequently　deformed　via　cold　rolling　and　annealing　(CRA).　The　effects　of　Si　content　and　annealing　temperature　on　the　microstructural　evolution　and　tensile　properties　of　the　alloys　were　systematically　investigated.　The　results　indicate　that　a　single-phase　FCC　structure　of　coarse-grained　FeCoCrNiMnSix　HEAs　was　obtained　after　homogenized　annealing　(HOA),　and　the　distribution　of　each　element　was　uniform.　When　the　molar　ratio　of　Si　was　increased　from　0　to　0.2,　the　strength　of　the　HOA　HEAs　increased　by　nearly　50%,　and　the　elongation　did　not　decrease,　largely　due　to　solid　solution　strengthening　and　the　reduction　in　stacking　fault　energy.　Conversely,　as　Si　content　increased,　the　recrystallization　ratio　decreased　during　annealing.　A　heterogeneous　grain　structure　composed　of　recrystallized　and　residual　deformation　regions　(high　density　of　dislocations　and　deformation　twinning)　was　obtained　by　changing　the　CRA　temperature　and　Si　content.　A　heterogeneous　grain　structure　of　CRA　HEAs　with　an　annealing　temperature　of　700　℃　and　Si　content　of　0.2　exhibits　approximately　fourfold　higher　yield　strength　(733　MPa)　compared　to　that　of　HOA　FeCoCrNiMn　HEAs　(185.27　MPa).　The　structure＇s　tensile　strength　and　ductility　were　measured　at　959　MPa　and　29.5%,　respectively.　The　high　strength　was　mainly　attributed　to　the　combined　effect　of　multiple　strengthening　mechanisms.　Heterogeneous　deformation-induced　strain　hardening　and　twinning-induced　plasticity　provide　good　ductility.　©　2022　Elsevier　B.V.