Uniaxial　tensile　behavior　of　concrete　plays　an　important　role　in　the　behavior　of　concrete　specimens　as　well　as　structural　elements.　A　2D　mesoscale　analysis　is　performed　to　investigate　the　fracture　process　of　concrete　subjected　to　uniaxial　tension　by　using　the　extended　finite　element　method.　The　concrete　considered　includes　the　hydrated　cement　paste,　aggregate　particles,　and　the　interfacial　transition　zones.　In　the　cracked　domain,　to　represent　the　discontinuities　of　a　displacement　field,　the　Heaviside　jump　function　is　added　to　the　common　finite　element　approximation　for　the　local　enrichment　based　on　the　framework　of　partition　of　unity.　A　user-defined　subroutine　for　the　extended　finite　element　method　is　implemented　with　FORTRAN　codes　and　embedded　into　the　commercial　software　ABAQUS.　The　failure　process　of　the　L-specimen　is　studied,　and　good　agreement　is　obtained　between　the　experimental　observation　and　the　present　simulation　results.　Based　on　the　extended　finite　element　method,　the　fracture　process　of　the　concrete　under　uniaxial　tension　is　investigated　subsequently.　The　influences　of　aggregate　distribution,　aggregate　size,　and　aggregate　shape　as　well　as　the　strength　of　interfacial　transition　zone　on　the　failure　process　and　the　global　deformation　process　of　concrete　are　analyzed.　The　crack　initiation,　propagation,　and　failure　mode　of　concrete　specimens　are　also　discussed　in　detail.　The　simulation　results　indicate　that　the　macroscopic　mechanical　properties　of　concrete　are　merely　dependent　on　the　aggregate　distribution,　but　dependent　on　aggregate　shape,　size,　and　strength　of　the　interfacial　transition　zone.