How to control the post-construction settlement of deep soft soil foundation in high-speed railway is a worldwide problem. Therefore, analysis of settlement monitoring data of 100 km subgrade during the operation period of 3 years based on the Shanghai-Nanjing inter-city high-speed railway is performed in this paper, and the post-construction settlement is divided into four grades which can be used to evaluate the settlement control effect. Combined with the sedimentation estimation, it is further divided into four states:stability, basic stability, critical overrun and overrun. Aiming at addressing the problems existing in the routine analysis method of post-construction settlement control of foundation treatment measures, the concept of "equivalent soft soil thickness" is proposed, which can quantitatively analyze the effect of post-construction settlement control of foundation treatment measures. Results obtained from the comprehensive analysis show that the post-construction settlement of the high-speed railway subgrade is positively related to the thickness of the weak soil. There exists a "critical" equivalent soft soil thickness in the different treatment measures, and the thickness of the equivalent settlement of the foundation in the pile-soil is 1.7 times of that of pile-raft composite foundation, and it is 2.2 times of pile-net composite foundation. Pile-plate structure treatment foundation is equivalent to weak soil thickness, and its corresponding post-construction settlement is only 59% of pile-raft composite foundation. In addition, the raft composite foundation is 76% of the pile-net composite foundation.