The physical properties of three different kinds of water under the action of an electromagnetic field and stirring are studied. The result shows that the surface tension coefficient, the viscosity and the density of water significantly change with magnetic induction intensity and magnetization time. This experimental law has also been reported in many other papers, but has not yet been explained. In the present paper, according to the molecular structure of water and characteristics of hydrogen bond, we further study the mechanism of magnetized water with the theories of thermology, electromagnetism and structural chemistry, and also investigate more extreme phenomena about surface tension coefficient, viscosity and density of magnetized water. It is found that the breaking of a large number of hydrogen bonds is due to the fact ther electrons states are affected by magnetic field or perturbation, and thus the interaction between electrons is influenced when the water solution is magnetized in a field of 200 mT above. As the formation conditions of hydrogen bond are easily satisfied, the breaking and the forming of the hydrogen bond of the liquid water coexiste at a certain temperature, and their occurence probabilities are alternated in magnitude in the magnetization process, resulting in more extreme phenomena. The change extent of physical quantity with random fluctuation depends on the strong or weak extent of the breaking and the forming of hydrogen bond.