The　surface　roughness　induced　by　geometric　irregularities　(asperities)　has　substantial　influence　on　the　contact　stiffness,　which　further　affects　the　working　performance　and　service　life　of　mechanical　equipment.　In　this　study,　an　elastic-plastic　contact　law　between　a　sinusoidal　asperity　and　a　rigid　smooth　flat　is　first　studied,　which　is　then　applied　on　a　statistical　model　to　simulate　the　contact　behavior　of　a　pair　of　18CrMo4　steel　surfaces　to　investigate　the　influences　of　morphology　parameters　on　the　contact　stiffness.　The　analysis　shows　that　smaller　shape　ratios　xi　and　larger　wavelengths　lambda　induce　larger　normal　contact　stiffness　K-n　for　surfaces　with　identical　roughness,　wherein　the　roughness　is　defined　by　the　mean　value　of　asperity　heights　R-a　and　the　standard　deviation　of　asperity　heights　R-q.　The　normal　contact　stiffness　increases　as　R-a　decreases　under　the　same　loading　conditions,　while　the　normal　contact　stiffness　increases　as　R-q　decreases　for　surfaces　with　a　fixed　R-a.　Besides,　the　normal　pressure　and　normal　contact,　stiffness　derived　from　the　proposed　contact　model　are　validated.　The　results　demonstrate　the　potential　of　the　proposed　model　in　contact　design　due　to　its　ability　of　establishing　the　relations　between　the　normal　contact　stiffness　and　surface　morphology　parameters.