To better apply low-field nuclear magnetic resonance (NMR) to the evaluation of the physical properties of the coal reservoirs, this work established the NMR porosity and permeability models for coals based on a large number of NMR experiments. For low rank coals, the T-2 distributions show continuous bimodal or trimodal characteristics; the relative amplitude (T-2 distributions amplitude per unit volume) of the flow space is up to 12%; while the relative amplitude of the adsorption space is only 0-2%. For medium rank coals, the T-2 distributions have a similar shape as those of the low rank coals; the relative amplitude of the flow space is 0-5%, and the relative amplitude of the adsorption space is 0-3%. For high rank coals, the T-2 distributions have two separated crests or a single peak; in these samples, the adsorption space is well developed with the relative amplitude up to 50%, and the relative amplitude of the flow space is 0-5%. High rank coals have the best developed adsorption space; in contrast, low rank coals have the largest flow space. Since coals with different ranks have different T-2 distributions and different amplitude, it is necessary to establish the NMR porosity and permeability models for coals with different ranks, respectively. Thus, we can accurately calculate the porosity and permeability of the coal in different metamorphic stage. Experimental results show that porosity and permeability parameters calculated by these models have a high correlation with the data measured by conventional methods.