Abstract: To investigate the stress-strain characteristics of lignin-treated silt, the cementation properties of lignin-stabilized soil are discussed based on the results of unconfined compression strength tests and the microstructural analysis. Based on the boundary surface plasticity theory, the parameters of hardening, stress dilatancy and destruction rate of bounding effect are proposed to develop a new boundary surface plasticity model for the lignin-treated silt considering cementation. The non-associated flow rule and the modified imaging rule are introduced to capture different failure modes of stabilized soil, and the meaning and calculation methods of the parameters are also explained. The characteristics of stress-strain, stress dilatancy and excess pore pressure change for the lignin-stabilized silt are analyzed based on the results of consolidation tests and triaxial compression tests in the laboratory, and the validity of the proposed model is also verified. The results show that the reason for the engineering properties of the improved silt is the cementation introduced by lignin. The yield stress and undrained shear strength of lignin-treated silt with additive content of 12% are increased by about 90% and 40%, respectively. The characteristics of stress dilatancy and excess pore pressure are different under different confining stresses. The model results are consistent with the laboratory test ones, and the model can successfully capture the characteristics of stress-strain. The proposed model has advantages of clear principle and simple parameters, and it may provide a theoretical basis for the numerical computation of stabilized soil.