Abstract: The dynamic characteristics of three kinds of Sands ware examined by means of dynamic triaxial tests. The results are summarized as follows: （1）shear modulus and damping ratio of saturated sands all decrease with the increase of pore water pressure. （ 2 ）shear modulus and damping ratio may be expressed as the functions of pore water pressure and shear-strain amplitude: G =f（u） · Gm（γ）, λ = g（u）·λm （λ）.From the test results the expressions of G-u and λ-u under the test condition are derived by separating variable. （ 3 ）the effect of sample films on test results is studied and analysed. With the effect of films modified, both shear modulus and damping ratio of the soil during liquefaction may be considered to approach zero.