Turfy soil in the seasonal frozen area is a special soil containing a large amount of undecomposed fiber residues formed by the accumulation of plant residues in the swamp environment under the action of oxidation and decomposition. The turfy soil fiber and its content have an important impact on the strength and deformation characteristics of turfy soil. At present， the research on the constitutive relationship considering the influence of fiber content on the strength and deformation characteristics of turfy soil is relatively scarce. The K-G constitutive model is widely used for nonlinear theoretical and numerical calculation analysis in geotechnical engineering because the model parameters can be directly connected with the bulk modulus and shear modulus of soil. Taking turfy soil with different fiber content as the research subject， the stress-strain curve of turfy soil was studied by triaxial shear test， and the nonlinear K-G model parameters of turfy soil were obtained. The linear function relationship between model parameters and fiber content was established. It can provide some guidance for actual highway construction.