Abstract: A series of undrained cyclic triaxial and bender element tests are carried out on sandy soils with three different particle size ratios by using the GDS cyclic triaxial apparatus with bender elements. The effects of fines content, density, initial effective confining pressure, sample preparation method and particle size ratio on liquefaction characteristics of sandy soils are analyzed. Whether the equivalent skeleton void ratio e* can reasonably and uniformly characterize the liquefaction resistance of the sandy soils under different initial states and different particle size ratios is discussed. The results show that e* can reasonably quantify the influences of low plastic fines content on liquefaction resistance CRR₁₅ of various sandy soils, showing a negative idempotent relationship between CRR₁₅ and e*. There is also a unique relationship between small strain shear modulus G₀ and e*, which indicates a unique relationship between CRR₁₅ and G₀. It provides a new empirical method for the evaluation of liquefaction resistance of the sandy soils. Meanwhile, the influences of the initial confining pressure and sample preparation method should be considered when e* is used to characterize the liquefaction resistance, especially for smaller void ratio and fines content. When it is less than 9.9, the particle size ratio χ has a great influence on the relationship between CRR₁₅ and e*, while it has a negligible effect when it is greater than 9.9. It is found that there is a unique relationship between equivalent relative density D_r* and CRR₁₅ for the tested three sandy soils, despite of the fines content and particle size ratio.