To understand the effect of eliminating collapsibility and the change of soil structure after soaking treatment in the process of treating collapsible loess foundation with pre-soaking method, the indoor collapsibility test and scanning electron microscope (SEM) scanning test were carried out after washing and losing water treatment of soil at different depths, and the collapsibility and SEM images of undisturbed loess and soaking losing water loess at various depths were obtained. The results show that the shallow and deep strata can be divided according to whether the overlying strata’s saturated self-weight pressure can reach the strata’s initial collapsible pressure. The place where the saturated self-weight pressure of the overlying strata can go is deep strata, and vice versa. However, with the increase of burial depth, the decrease of porosity continues to increase, and the increase of initial collapsibility pressure tends to a fixed value and does not increase.