The foundation soil of the buildings and structures is often in complex initial stress states. The dynamic torsional shear triaxial tests are carried out on undisturbed and remodeling loess under different complex initial stress states by using the remolded DTC-199 torsional cyclic load triaxial apparatus, and the effects of each complex initial stress state parameter on dynamic shear modulus of loess are discussed. Results show that, other conditions being the same, the influence of angles of initial principal stress α0 on dynamic shear modulus Gd of loess show a trend of the bigger α0 is, the smaller Gd is. The effect laws of efficient of initial intermediate principal stress b0 on Gd of loess are not obvious. When the dynamic shear strain is larger, the bigger initial deviator stress ratio η0 is, the smaller Gd of loess is. The influence of initial average principal stress pm0 on loess is significant. The bigger pm0 is, the bigger Gd of loess is. Gd of undisturbed loess is greater than that of remodeling loess under the complex initial stress states.