Abstract: An experimental investigation was presented to study the failure criterion of strain for natural and remolded soft clay of Xiaoshan.Compared were the cyclic strengths defermined with three failure criteria of strain,including 5% and 10% and that proposed by the author.There was obvious influence on cyclic strength defermined with different failure criteria of strain when failure cycle number was relatively small.While the number was large enough,the difference befween the cyclic strengths defermined with different failure criteria of strain decreased with increase of failure cycle number and a minimum cyclic strength was obtained.The confining pressure had an important influence on the cyclic strength of structural soft clay.The cyclic strength of natural soft clay was higher than that of remolded soft clay when confining pressure was smaller than the structural yield stress.Otherwise,the former would be close to the latter.