Current　meso-mechanics　models　cannot　reflect　the　influence　of　model　sizes　and　aggregates　gradation　on　microstructure　heterogeneity　of　concrete　appropriately,　therefor　the　meso-element　equivalent　models　were　established,　composed　of　aggregates,　mortar　matrix　and　interfacial　transition　zones.　The　mechanical　properties　of　each　element　were　processed　equivalently　based　on　the　Voigt　parallel　model.　The　distribution　type　of　element　elastic　modulus　was　supposed　as　the　Weibull　distribution,　and　the　mesh　scale　of　meso　element　for　different　aggregates　gradation　and　model　sizes　was　analyzed.　The　heterogeneous　distribution　of　element　elastic　modulus　was　used　to　represent　the　microstructure　heterogeneity　of　concrete.　The　influence　of　model　sizes　and　aggregates　gradation　on　microstructure　heterogeneity　of　concrete　was　studied,　and　the　effect　of　microstructure　heterogeneity　on　the　strength　and　fracture　modes　of　concrete　was　analyzed.　The　analytical　results　indicated　that　the　element-mesh　scale　increases　with　the　increase　of　the　model　sizes　and　the　raise　of　aggregates　graduation.　The　microstructure　heterogeneity　of　concrete　weakens　gradually　with　the　increase　of　the　model　sizes;　however　strengthens　with　the　raise　of　aggregates　graduation.　The　strength　of　concrete　decreases　and　fracture　bands　extend　more　extensively　with　the　raise　of　microstructure　heterogeneity.　©　2017,　The　Editorial　Board　of　Journal　of　Basic　Science　and　Engineering.　All　right　reserved.