Abstract: It is of great significance to understand the distribution and dynamic transport characteristics of polymorphic water in the coal-water two-phase system for estimating the water injection effect of coal seam, and the development and utilization of coal-bed methane. With the calibration of the moisture in different state relaxation times in porous media, the test coal samples were infiltrated and the CPMG sequence test was conducted with the low-field nuclear magnetic resonance experimental system. Based on the results of coal polymorphic water distribution, the quantitative relationship between the relaxation characteristics of free-state water and the wettability of coal bodies was established. According to the kinetic theory, the tendency of water peak area of the adsorption state of coal with time was studied, and the microscopic mechanism between coal reservoirs and water molecules was revealed. The brief conclusions are described below. The relaxation time corresponding to the water peak in adsorbed form is between 0.1 and 10 ms. The relaxation time of pure free-state water peak is in the range from 800 to 10 000 ms, and the relaxation rate of free-form water in porous media will be accelerated. The bound water peak is located in the middle of the adsorbed water and the free-form water peak. The relaxation characteristics of free water peaks of different coal samples are closely related to their own wettability. The faster the relaxation rate of coal-like free-state water with better wetting capacity, the shorter the relaxation time, and the stronger the ability to shift to the left of the corresponding peak. There is a quantitative relationship between the contact angle θ and the infiltration time t required for the closure of the free-state water peak of the coal sample and the relaxation time T₂ corresponding to the apex of free-state water peak at the corresponding time t,which is consistent with θ=51lg T₂+2.4t^0.3-87. The adsorbed water peak area of coal can be used to evaluate the effect of water injection and dust reduction in coal seams. The law of the peak area of water in the adsorption state with time conforms to the first-level adsorption kinetic model, indicating that there is only one adsorption site on the surface of pulverized coal. The adsorption process of water molecules in the coal body is composed of two parts. The main adsorption process is controlled by diffusion and occurs on the polar functional groups on the surface of the coal body. The secondary adsorption occurs on the adsorption sites formed by the adsorbed water molecules in the outer layer of the coal, and the water condensation formed in this process is the cause of water lock effect. Whether the water locking effect can be generated is greatly related to the wetting ability of the coal sample itself.