Lanzhou loess is divided into dry patter, wet patter, and saturated patter according to original water content.The three patterns are studied by using torsion shear apparatus. The constitutive relationship between dy namic stress and strain,the dynamic properties of the damping ration, and the strength of the three patters are studied. The dynamic strength indexes are presented for the cycle time of 10,20,and 30.The study indicates that the curve for stress and strain of the three patterns is a hyperbolic curve; the relationship between damping ration and dynamic strain is linear; and dynamic strength is affected by consolidation stress. At the same time, the dy namic strength indexes change with the cycle time, but change in friction angle is less than that in cohesive strength