The　carbon-doped　Fe50Mn30Co10Cr10　HEAs　with　excellent　cryogenic　mechanical　properties　were　prepared　by　powder　metallurgy,　and　their　tensile　deformation　behavior　and　strain-hardening　mechanism　were　investigated.　The　yield　strength　of　the　HEAs　at　77　K　improved　from　489.7　to　1087.0　MPa　as　the　carbon　content　increased　from　0　to　3　at.　%,　which　mainly　stems　from　the　increased　lattice　friction　caused　by　the　addition　of　carbon　and　the　cryogenic　environment;　the　ultimate　tensile　strength　of　the　HEAs　doped　with　2　and　3　at.　%　carbon　reached　1.2　and　1.4　GPa,　respectively,　while　the　elongation　to　fracture　reached　31.6　%　and　16.8　%,　respectively,　which　is　mainly　attributed　to　the　joint　activation　of　microbands,　twinning,　and　HCP　phase.　The　deformation　mechanism　gradually　changed　from　deformation-induced　phase　transformation　to　microbands　and　twinning　with　increasing　carbon　content　under　cryogenic　conditions.　This　study　provides　a　meaningful　reference　for　the　design　and　development　of　powder　metallurgy　HEAs　with　excellent　performance　in　cryogenic　applications.　©　2023　The　Authors