This　paper　summarizes　an　engineering　experience　of　solving　the　problem　of　thermal　cracking　in　mass　concrete　by　using　a　large　project,　Zhongguancun　No.1　(Beijing,　China),　as　an　example.　A　new　method　is　presented　for　controlling　temperature　cracks　in　the　mass　concrete　of　a　foundation.　The　method　involves　controlled　cycles　of　water　circulating　between　the　surface　of　mass　concrete　foundation　and　the　atmospheric　environment.　The　temperature　gradient　between　the　surface　and　the　core　of　the　mass　concrete　is　controlled　at　a　relatively　stable　state.　Water　collected　from　the　well-points　used　for　dewatering　and　from　rainfall　is　used　as　the　source　for　circulating　water.　Mass　concrete　of　a　foundation　slab　is　experimentally　investigated　through　field　temperature　monitoring.　The　temperature　field　of　the　mass　concrete　during　the　entire　process　of　heat　of　hydration　are　analyzed　in　detail.　The　proposed　method　provides　an　alternative　practical　basis　for　preventing　thermal　cracks　in　mass　concrete.