Hardening soil model with small strain stiffness (HSS model) can reflect the nonlinear characteristics and stress correlation of the small strain phase of soil, which has been widely used in deep foundation pit, but there is a lack of systematic research on the parameter determination methods owing to the numerous parameters. Sensitivity analysis of HSS model parameters was carried out by numerical simulation method. Based on a large number of statistical research results, the nonlinear relationship between soil parameters and void ratio was established and verified by deformation analysis in two deep foundation pit projects. The results showed that the sensitivity of the reference dynamic shear modulus was the highest and the sensitivity of the reference tangent modulus was the lowest in the numerical analysis of the foundation pit, the established nonlinear relationship could better reflect the correlation between the soil modulus and the void ratio, and there was a good agreement between the calculated and measured values of the enclosure lateral displacement, which verified the applicability of the proposed parameter determination method and could provide reference for related projects.