Abstract: In order to investigate the liquefaction resistance CRR of fine-coarse-grained soil mixtures, a series of undrained cyclic triaxial tests are performed on the fine-coarse-grained soil mixtures with different values of fines content FC and relative density D_r. According to the theory of intergrain contact state, the mixtures are categorized as coarse-like soil, intermediate behavior soil and fines-like soil. The skeleton void ratio e_sk is used as the grain contact density index to describe the intergrain contact state which composes the skeleton of mixtures, and the parameters b and m are used to characterize the contribution of the fines and the coarse grains to the transition between coarse-like and fines-like behaviors in mixtures. The test results show that as FC increases, the CRR of mixtures with the same D_r decreases first, and thereafter it remaines constant. In addition, the CRR of mixtures with different values of FC and D_r decreases with the increase of e_sk. Moreover, the test data obtained in this study reveal that e_sk can be used as the index to uniquely evaluate the CRR of mixtures, and a power relationship between a decrease in CRR and an increase in e_sk is then obtained.