Abstract: Inverted siphon is an important cross-building project for water diversion and irrigation. 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 basic theories of temperature field and stress field of concrete, the 3-D FEM is adopted to simulate the stresses field of Qinhe river Inverted siphon during construction. Through analyzing the time-space variation law, it is found that cracks easily appear. In the middle section of the South to North Water Transfer Project，for the first time, the quality of concrete has been improved obviously through the method of external insulation board.?The results show that the safety coefficient of tensile strength of concrete can be greater than 1.6, so it deserves to be popularized for other engineering applications.