The liquefaction of saturated sand is due to a negative dilatancy. In the cyclic triaxial test, a part of pore water squeezed from sample is transformed into the reduction of membrane penetration and so the perfect undrained test can not be performed. Consequently, the liquefaction resistance obtained by the cyclic triaxial test is evaluated apparently larger than true value. In this paper, the method of correction of the liquefaction resistance is proposed by consideration of various experimental results. It is clear that the volume change of sample obtained by the undrained cyclic triaxial test is nearly equal to the expansive volume change of sample due to the decrease of effective stress. According to this relation, we considered that the liquefaction resistance obtained by the cyclic triaxial test can be corrected by means of the obtaining volumetric strain of sand structure concerned with the increase of pore pressure as the difference between expansive volume change and volume change been equivalent to the membrane penetration. This procedure is explained in Fig. 9 schematically.