In practical projects, foundations or roadbeds soil is usually in complex initial stress states, and deformation and settlement may happen caused by earthquakes or other dynamic loadings. Since conventional laboratory soil test cannot authentically reproduce dynamic behaviors of soils under complex initial consolidation stress conditions, dynamic deformation behaviors of compacted loess is conducted under complex initial stress conditions through remodeled DTC-199 torsional cyclic load triaxial apparatus. The paper systematically investigated the effects of different initial stress state, such as average principal stress p0 , the angle of initial principal stress α0 and the initial intermediate principal stress coefficient b0, etc. on dynamic shear modulus Gd and damping ratio λ. Results show that: (1) To the same γd , Gd increases with the increase of p0 but the α0 and b0 have no influence on Gd. (2) The α0 has a little influence on λ and the p0 and b0 have no influence on λ.