The　capacity　of　absorbing　carbon　atoms　strongly　depends　on　the　alloy　elements　in　steels.　The　carbon　content　of　carburized　layer　in　22Si2MnCrNi2Mo　steel　with　more　non-carbide　forming　elements,　Si,　Mn,　is　only　0.65%,　but　that　in　35CrMoV　1.05%.　The　results　from　the　impact　wear　tests　indicates　that　the　impact　wear　rate　decreases　first　and　then　increases　with　the　increase　of　carbon　content　in　carburized　layers.　The　minimum　of　the　wear　rates　occurs　in　0.82%　C.　The　deformation-induced-M-transformation　of　the　retained　austenite　in　impact　wear　process　brings　about　an　additional　consumption　of　applied　impact　energy,　which　could　give　a　decrease　of　wear　rate　of　carburized　layers.　A　exponent　relationship　between　impact　wear　rate　and　M-transformation　energy　has　been　obtained.