This　paper　presents　experimental　and　meso-scale　modelling　studies　on　the　combined　effects　of　strain-rate　and　specimen　size　on　uniaxial　compressive　failure　behaviour　of　concrete.　A　series　of　uniaxial　compressive　tests　and　meso-scale　simulations　were　conducted　on　concrete　with　various　specimen　sizes　under　different　strain-rates　covering　the　strain-rate　range　of　seismic　load,　with　special　focus　on　the　quantitative　contribution　of　end-friction　to　compressive　strength　and　its　corresponding　strain-rate　effect　as　well　as　size　effect.　Results　indicate　that　the　uniaxial　compressive　failure　with　end-friction　follows　an　hourglass　failure　pattern　while　that　without　end-friction　exhibits　a　columnar　failure　pattern.　The　end-friction　effect　can　form　different　confined　zone　distributions　for　various　sized　specimens,　which　can　cause　the　contribution　of　end-friction　to　compressive　strength　is　size　dependent　as　well　as　enhance　the　influence　of　specimen　size　on　static　and　dynamic　strength.　The　contribution　proportion　of　end-friction　to　compressive　strength　is　around　20　similar　to　25%.　Moreover,　larger-sized　specimen　performs　a　stronger　strain-rate　effect　and　the　increasing　strain-rate　can　weaken　the　influence　of　specimen　size　on　the　real　compressive　strength.　The　proposed　real　DIF　empirical　formula　considering　the　size-dependency　(covering　the　low　strain-rate　range)　can　well　estimate　the　strain-rate　effect　for　concrete　with　different　sizes,　which　can　provide　a　valuable　reference　for　the　numerical　calculation　of　dynamic　mechanical　response　and　the　safety　design　of　concrete　structures.