In　this　paper,　the　validity　and　performance　of　base　force　element　method　(BFEM)　based　on　potential　energy　principle　was　studied　by　some　numerical　examples.　And　the　BFEM　on　damage　mechanics　is　used　to　analyze　the　size　effect　on　tensile　strength　for　recycled　aggregate　concrete　(RAC)　at　meso-level.　The　recycled　aggregate　concrete　is　taken　as　five-phase　composites　consisting　of　natural　coarse　aggregate,　new　mortar,　new　interfacial　transition　zone　(ITZ),　old　mortar　and　old　ITZ　on　meso-level.　The　random　aggregate　model　is　used　to　simulate　the　meso-structure　of　recycled　aggregate　concrete.　The　size　effects　of　mechanical　properties　of　RAC　under　uniaxial　tensile　loading　are　simulated　using　the　BFEM　on　damage　mechanics.　The　simulation　results　agree　with　the　test　results.　This　analysis　method　is　the　new　way　for　investigating　fracture　mechanism　and　numerical　simulation　of　mechanical　properties　for　RAC.