Efficiency of building passive cooling is based on the water absorption characteristics. Illustrated by the example of porous firing clay tiles, test methods are different between national and international standards. Capillary water absorption coefficients and capillary saturated water contents of three kinds of porous face tile are measured through partial immersion method referred to the international standard. The results show that both porosity/capillary absorption coefficient and porosity/capillary saturated water content have a linear positive correlation. Water contents after 24 hours absorption are measured through integral immersion method referred to the national standard, and vacuum saturation method. The results are compared to those abtained through partial immersion. It is showed that the results of partial immersion is less than the results of integral immersion by 3.25%, and less than the results of vacuum saturation by 21.58%. The result shows that higher capillary water absorption coefficients means higher capillary saturated water contents. The corresponding kind of tile is more suitable for passive cooling. For the test method, partial immersion is more appropriate than integral immersion. Repeatability errors of all the tests are under 2.40%, showing high precisions.