In　this　study,　a　three-dimensional　mesoscopic　numerical　model　considering　concrete　heterogeneity　and　explicit　modelling　of　basalt　fibers　was　established　to　simulate　the　static　and　dynamic　split-tensile　failures　of　basalt　fiber-reinforced　lightweight　aggregate　concrete　(BFLAC),　with　a　special　focus　on　the　influences　of　structure　sizes　(D　=　100,　200,　300　and　400　mm),　basalt　fiber　contents　(V-f　=　0.1　%,　0.2　%　and　0.3　%),　fiber　lengths　(L-f　=　6,　12,　18,　24　mm)　and　loading　strain　rates　(epsilon　=　10(-5)/s　similar　to　100/s)　on　split-tensile　failure　patterns,　deformation　characteristic　and　failure　strengths.　Simulation　results　indicate　that　as　the　fiber　length　increases,　split-tensile　strength　of　BFLAC　enhances　first　and　then　remains　unchanged.　As　the　fiber　content　increases,　both　static　and　dynamic　split-tensile　strengths　enhance,　showing　a　fiber　reinforcement　effect　which　increases　with　the　rising　strain　rate　rise　and　reaches　a　threshold　when　the　strain　rate　exceeds　1/s.　Under　static　and　low　strain　rates,　the　size　effect　on　split-tensile　strength　of　BFLAC　is　reduced　by　the　addition　of　basalt　fiber　content;　while　there　is　a　reverse　size　effect　under　high　strain　rates　and　it　is　strengthened　with　the　increasing　fiber　content.　Besides,　the　strain　rate　effect　of　BFLAC　is　stronger　with　the　increasing　basalt　fiber　content.　A　unified　TDIF　formula　of　BFLAC　considering　the　influence　of　basalt　fiber　content　was　proposed,　which　can　provide　a　valuable　reference　for　the　dynamic　performance　simulations　and　calculations.