Since the Cambridge elastoplastic model was proposed in 1963, modern soil mechanics has made significant progress. Traditional methods such as the Boussinesq equation or limit equilibrium methods often regard soil as a linear elastic or rigid plastic material, ignoring the true stress-strain relationship of soil. To more scientifically and reasonably reflect the actual stress state of the soil, based on the generalized potential theory proposed by Yang Guanghua in 1993, a simplified double potential surface model of the generalized potential theory (σ1-σ3) is proposed using mathematical principles. Through triaxial tests and compared with traditional models such as the Duncan-Chang model and the Cambridge model, the σ1-σ3 double potential surface model more accurately approaches the actual experimental data, better predicts the stress-strain relationship of soft soil under different stress paths, and has model parameters that are easier to obtain.