The　size　effect　of　the　nominal　strength　of　reinforced　concrete　columns　is　caused　mainly　by　1)　the　heterogeneity　of　concrete　itself,　and　2)　the　complex　mutual　effects　between　steel　rebar　and　the　surrounding　concrete.　Besides,　the　slenderness　effect　is　another　brutal　factor　that　could　affect　the　failure　pattern　and　the　load　capacity　of　RC　columns.　Considering　of　the　mesoscopic　heterogeneity　of　concrete　and　the　nonlinear　bond-slip　behavior　between　concrete　and　steel　rebar,　a　meso-scale　mechanical　analysis　model　for　the　study　of　mechanical　properties　and　failure　behavior　of　RC　columns　subjected　to　axial　compressive　loading　is　set　up.　First,　the　mechanical　parameters　of　the　concrete　meso　components　are　confirmed　by　an　inversion　method　based　on　the　simulation　of　compressive　mechanical　properties　test　of　a　concrete　specimen.　Then,　the　damage　process　of　the　RC　columns　with　different　slenderness　ratios　subjected　to　axial　compressive　loading　is　simulated.　The　results　indicate　that,　the　RC　columns　with　low　slenderness　ratios　exhibit　compression-shear　failure　under　axial　compressive　loading.　The　RC　columns　with　high　slenderness　ratios　exhibit　buckling　failure,　and　the　failure　zone　concentrates　into　the　ends　of　the　column　due　to　the　end　effect.　The　nominal　strength　pronounces　stable　value　as　the　slenderness　ratio　is　smaller　than　9,　and　it　decreases　rapidly　when　the　slenderness　ratio　exceeds　9.　©　2016,　Science　Press.　All　right　reserved.