Abstract: The coefficient of lateral earth pressure at rest K₀ of Shanghai soft clay is measured by the GDS stress path triaxial device. The shear wave velocity and the corresponding small strain shear stiffness at K₀ state are also determined by the bender elements planned in the triaxial apparatus. The functional relationship between the maximum shear modulus G₀ and the isotropic confining pressure is established, and then the functional relationship between G₀ and K₀ is deduced. The possibility of using G₀ to calculate K₀ is investigated. Meanwhile, the value of G₀ at isotropic stress state is also measured and that of K₀ is back calculated based on the values of G₀ at isotropic stress state and K₀ stress state. The results indicate that the dissipation of the excessive pore water pressure during the K₀-measurement is very important to obtain the reliable value of K₀. Meanwhile, the back calculated values of K₀ based on the G₀-measurement agree well with the directly measured ones, which indicates the feasibility of K₀-determination based on the field shear wave velocity.