On the basis of the molecular dynamics of wood components, the effects of adsorption water molecules on the change of relaxation behavior were examined for wood specimens with various moisture contents using the low of mixture and stretched-exponential function (so-called the Kohlrausch-Williams-Watts (KWW) function). The KWW function has two parameters: the characteristic relaxation time and a parameter related to the dispersion of the relaxation time. Both parameters and the relaxation modulus at time 10 s, E(10), could be separated into three regions corresponding to moisture contents of 0-0.05, 0.05-0.10, and greater than 0.10. Experimental results provided a consistent explanation for the relationships between the isotherm curve analysis of wood, the dielectric relaxation behavior of adsorption water molecules, and the mechanical relaxation behavior of wood.