Abstract: In the project of water transferring from south to north of China (middle route), there are two large tunnels installed in the sand layers under the Yellow River bed. This paper deals with the problems of possible liquefaction and the depth of influence for these sand layers under 7 degree earthquake. The samples for dynamic tests are disturbed and undisturbed, which are taken from tunnel site by drilling.The depth of liquefaction in sand layer is estimated using different method. The anti liquefaction property for the sand sample compacted to higher density is also investigated. Finally, the vibrating acceleration of shield machine is measured to discuss the possibility of liquefaction during construction.