Due to a build-up of excess pore water pressure and a reduction in the effective stress, saturated clay is characterized by nonlinearity, hysteresis of stress-strain relationship, and degradation of stiffness and strength during undrained cyclic loading. This paper illustrates that the modified mixed hardening model considering stiffness and strength degradation is more reasonable by force of contrast. And the data obtained from dynamic tri-axial tests and published studies are compared to investigate various modulus degradation laws. It is verified that different laws adopted according to the clay property can capture complex behaviors more accurately.