With the aid of the N2 isothermal adsorption technology, the authors calculated the specific surface area and the pore radius distribution of sepiolite, zeolite diatomite and attapulgite by using the BET method, and the results showed that the specific surface areas were 81.56, 2.46, 1.68 and 187.70 m2/g, whereas the pore radius distribution values were 8.53, 18.20, 31.57 and 11.79 nm, respectively. Their maximal absorbing moisture values were 5.6%, 2.2%, 1.8%and 6.0%, respectively, at 25℃ and 75% relative humidity. After the saturation of the absorbing moisture, the samples of these four kinds of minerals were put in the environment of 25℃ and 35% RH to make moisture discharge. The capacities of desorbing moisture were 4.4%, 1.8%, 1.6% and 5.0%, respectively. A comparison of the specific surface area and pore radius distribution of the four inorganic porous minerals with their capacities of absorbing and desorbing moisture in the air demonstrates that the sample whose specific surface area is relatively large and whose pore radius distribution is consistent with the computation result of Kelvin formula, such as sepiolite, has comparatively strong absorbing and desorbing moisture capacity in the air.