The　reliable　design　of　reinforced　concrete　(RC)　structures　against　external　mechanical　forces,　including　earthquake-induced,　impact　and　other　types　of　forces,　necessitates　a　clear　understanding　of　the　mechanical　behavior　and　size　effect　of　moderate　high-strength　RC　structural　members　under　cyclic　loading.　This　study　presents　the　results　of　an　experimental　study　on　a　series　of　geometrically　similar　moderate　high　strength　RC　columns　under　monotonic　and　cyclic　axial　compression.　A　total　of　16　moderate　high-strength　RC　columns　with　different　structural　dimensions　(in　the　ratio　1:2:3:4)　were　tested.　The　cross-sectional　size　of　the　columns　was　between　200　mm　and　800　mm,　and　the　length　varied　from　600　mm　to　2400　mm.　The　overall　mechanical　performances　of　the　moderate　high-strength　RC　columns,　including　the　failure　patterns,　the　hysteretic　curves,　the　nominal　compressive　stress-strain　relationships,　the　peak　load-carrying　capacity,　the　energy-dissipation　capacity,　the　nominal　compressive　strength,　the　concrete　softening　behavior　and　the　buckling/necking　of　steel　rebar　were　observed　and　explored.　The　test　observations　indicate　the　existence　of　size　effect　in　relatively　larger-sized　moderate　high-strength　RC　columns　under　both　monotonic　and　cyclic　axial　compression,　and　the　RC　columns　under　cyclic　loading　pronounce　a　more　obvious　size　effect.　It　is　found　that　the　bi-logarithmic　plots　of　nominal　compressive　strengths　for　different　moderate　high-strength　RC　columns　follows　closely　the　＂size　effect　law　(SEL)＂　proposed　by　Baiant.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.