If the boundary conditions are not considered in the limit load analysis of the soft foundation reinforcement section, the analysis results will be deviated, and the hidden danger will easily occur during the train operation. Therefore, a new limit load analysis method for the soft foundation reinforcement section of high-speed railway is proposed, and its effectiveness is analyzed through experiments. Considering the boundary conditions of the calculation model, the ultimate load calculation scheme is designed, the basic coordinate system in the limit equilibrium state is established, and the stress component in the yield state is analyzed. By solving the stress equations, the load displacement curve of the reinforced section of soft foundation can be obtained in the calculation software. The engineering application results show that the load displacement curve obtained by the proposed method is closer to the actual situation, and the analysis results are more accurate.