In view of the problem of mass concrete cracks during construction, the corresponding measures and methods are put forward. Generally speaking, the difference between the internal and external temperature and the basic difference of temperature are considered as the main factors influencing the phenomena. Under the FEM is adopted to simulate the stresses field of Inverted siphon during construction. Through analyzing the time-space variation law, it is fund that cracks easily appear. In the part of the middle line of the South-North Water Transfer Project£¬the quality of concrete surface of ¢ñsection in Jiaozuo has been improved obviously through the method of external insulation board, so it deserves to bepopularized.