Abstract: Abstract: The application of magnetic water in the agriculture and water treatment has been getting a lot of attention. However, it is still difficult to quantify the effect of magnetic treatment on the liquid water structure. In this study, the effects of magnetic treatment on the internal energy, surface entropy, and free water ratio of liquid water were studied by the analysis of viscosity, surface tension, and the full width at half amplitude of 17O-NMR. Further more, the analytical hierarchy process (AHP) was introduced to integrate the assessment of the effect of magnetic treatment on the cluster structure of water, and the integrated assessment index (IAI) was established to quantify the effect of magnetization on the liquid water. The viscosity of magnetic water increased with increasing the effective magnetic treatment time and had an amplification of approximately 10% when the effective magnetic treatment time was 13 minutes, and the internal energy of water decreased with increasing the effective magnetic treatment time. The surface tension and surface entropy of magnetic water decreased sharply with the the effective magnetic treatment time ranged from 1 minute to 13 minutes. The full width at half amplitude of 17O-NMR of purified water did not change when the effective magnetic treatment time was 1 minute but increased with an increasing the effective magnetic treatment time when the effective magnetic treatment time was higher than 1 minute, and the concentration of the hydrogen-bonded water increased. These results indicated that magnetic treatment promoted the formation of water clusters, and altered their distribution such that larger clusters were formed. This could be attributed to an increase in the intermolecular interactions of magnetic field treated water. In addition, according to the theory of AHP, an integrated model to assess the effect of magnetic treatment on the cluster structure of liquid water had been established as follows. The first step was to create a hierarchy model. To obtain the coincident magnitude of the indices, a normalizing method was applied to the indices (the internal energy, EI; surface entropy, SI; the free water ratio of liquid water, CI). The normalization method assumed all three indices of water to be 1 when the effective magnetic treatment time was maximum (13 minutes). The second step was to determine the pairwise comparison matrix for three indices. This problem involved a 3×3 reciprocal matrix, and the rule for determining pairwise comparison matrix had been summarized. The third step was the consistency measurement of the matrix just established. The fourth step was to calculate the weights of variables. According to the AHP theory, a normalized eigenvector corresponding to the maximum eigenvalue of the matrix just established will be the weight vector of the variables. The last step was to calculate the integrated assessment index (IAI). Therefore, the IAI value of magnetic water with any magnetization time can be calculated. The IAI values of the magnetic water increased linearly with increasing the effective magnetic treatment time, this result indicated that this method proposed a useful, reasonable, and acceptable method for the assessment of the effect of magnetic treatment on the cluster structure of water. The IAI values of magnetic water obtained by using the AHP are usefulness to study the application of magnetic water in the agriculture and water treatment.