Abstract: Soft soil has the characteristics of low strength, large susceptibility to disturbance, high compressibility and sensitivity. Undisturbed soft soil is often faced with the problems of difficult sampling, difficult preservation and transportation, which brings difficulties to the development of relevant laboratory model test research. In order to ensure the reliability and authenticity of the indoor model test, it is necessary to study the variation patterns of the physical and mechanical parameters of model soft soil prepared from similar materials, and prepare the soft soil used in the model test. In this paper, kaolin, bentonite and fly ash are used as raw materials for preparing model soft soil. The model soft soil samples with different proportions are designed and prepared by orthogonal test method. The liquid and plastic limit, direct shear and resonance column tests are carried out to obtain the physical and mechanical parameters of model soft soil under different proportions. The test results show the influence of each material on the different physical and mechanical parameters of the model soft soil. The recommended ratio of the model soft soil similar to the physical and mechanical parameters of the undisturbed soft soil in Tianjin Binhai area is obtained, and the model soft soil database is established. The physical and mechanical parameters of the model soft soil prepared according to the ratio scheme can basically meet the requirements of soil model tests.