Concrete　was　assumed　to　compose　of　aggregate　particles　and　a　mortar　matrix,　and　the　concrete　unit　was　processed　equivalently　based　on　the　Voigt　parallel　model　in　the　paper.　The　distribution　of　equivalent　elastic　modulus　of　a　meso-unit　was　studied,　based　on　the　Weibull　distribution,　and　a　graphical　method　and　the　stepwise　regression　were　applied　to　optimizing　the　estimated　parameters.　Furthermore,　the　validity　of　the　assumed　distribution　was　examined　by　the　Kolmogorov　test.　The　statistical　parameter　of　element　Young＇s　modulus　with　different　element-scale,　and　the　spatial　distribution　randomness　of　aggregate　were　studied　in　the　paper.　The　problem　on　material　characteristic　element　scale　of　concrete　of　different　grade-level　was　analyzed　at　the　end　of　the　paper.　The　analytical　results　indicate　that:　1)　the　form　and　the　parameters　of　random　distribution　of　elastic　modulus　of　a　concrete　meso-scale　unit　have　size　effects,　and　not　fully　obey　the　Weibull　distribution.　2)　the　variability　of　elastic　modulus　of　a　concrete　meso-element　associates　with　scales;　and　the　variability　increases　firstly　and　tends　to　be　stable　gradually　with　the　decrease　of　element　size,　which　reflects　the　facts　that　there　exists　a　reasonable　representation　of　non-uniform　degree　of　concrete　at　meso　level.　The　reasonable　scale,　i.e.　the　variation　coefficients　tending　to　the　inflection　point　of　a　smooth　transition　to　the　corresponding　scale,　is　defined　as　a　characteristic　element　scale.　3)　The　characteristic　element　scale　of　concrete　material　on　two-grade,　three-grade　and　four-grade　are　10mm,　15mm　and　18mm,　respectively.　4)　The　spatial　distribution　randomness　of　aggregate　has　little　effects　on　random　distribution　properties　of　elastic　modulus　of　a　concrete　meso-unit.