For the problem that there exist large calculation errors of the collapse deformation of foundation evaluated by the current "Code for Building in Collapsible Loess Areas", the in-situ test pit immersion test at Hongqing Station of Xi’an Metro, located in the self-gravity collapsible loess site, was carried out. Through the numerical analysis method, the actual vertical stress of the base distribution of different buried depth stations was analyzed by simulating the construction process of the station, and the unloading characteristics under the foundation of the station were revealed. The vertical compression stress distribution function under the foundation and enclosure structure of different buried depth stations is established. Based on the elastic solution, the calculation formula of the actual vertical compressive stress of loess strata varies with buried depth was established. Through the relationship between structural compression yield stress and comprehensive physical characteristic quantity, and the relationship between compressed pore ratio divided by initial pore ratio and compression stress and structural compression yield stress ratio, a method for evaluating the collapsibility of submerged saturated loess structure failure is established. Compared with the results of field test, the reliability of the evaluation method is verified. It has a certain reference significance for the prediction of collapsible deformation and the reasonable determination of foundation treatment depth in the design and implementation of urban rail transit engineering in loess region.