Soft soil is widely distributed in China. To ensure the high-speed and stable operation of trains, there are strict requirements for settlement deformation control of railway subgrades on high-speed railways. However, due to the lack of mature and reliable theories for calculating the settlement of soft soil subgrades, many high-speed railways with soft soil subgrades that have been built and put into operation in China have experienced excessive settlement deformations, which seriously threaten the operational safety of high-speed railways. In recent years, our research group has conducted in-depth studies on the theory of settlement calculation for soft soil subgrades by combining multiple projects such as the Ministry of Railways' "CFG Pile Composite Foundation Settlement Calculation Theory and Design Method," "Low Embankment Composite Foundation Settlement Deformation Law and Design Method," and the 863 Plan Project "Design Theory and Method for Uneven Settlement of Railway Subgrades under High Frequency and Heavy Load Conditions." Based on the study of settlement deformation laws of soft soil foundations, roadbed bodies, and the action of train dynamic loads, A set of relatively systematic soft soil subgrade settlement calculation methods has been proposed, especially for the widely used pile network and pile raft structures on ballastless track subgrades of high-speed railways. A settlement calculation method based on the combined stress of Mindlin-Boussinesq is established; for low embankments of soft soil subgrades that are prone to excessive additional deformation under the long-term action of train dynamic loads, a long-term deformation calculation method combining dynamic implicit and static creep considering the number of high cycle dynamic load repetitions is proposed. The research results have been applied in the construction of multiple high-speed railway projects.