The aperture and its distribution plays a remarkable role in permeation behavior, infiltration rate and filtration character of porous bodies. The methods in common use for determining the aperture and its distribution of porous materials are introduced, which include the direct observation from cross-section, the gas-bubble method, the permeation method, the mercury method, the gas-adsorption method, the liquid-liquid method, the suspension-filtration method, the X-ray small-angle scattering method, and so forth; and several measuring methods are compared with one another.