In loess formations, multiple layers of reddish ancient soil often alternate. Due to their relatively high hardness, they are resistant to collapsing when exposed to water, which significantly impacts the measurement results of the collapsibility of loess formations. However, there is currently a lack of research on the controlling role of ancient soils in collapsibility, leading to a lack of theoretical basis for making scientific decisions on the collapsibility of geological formations.To address this gap, this study compiled the results of inundation tests in the Loess Plateau region, analyzed the indoor and outdoor differences in collapsibility characteristics in different areas, and focused on large-scale inundation tests in two experimental sites in Xi'an. Various aspects were measured under different test conditions, including moisture diffusion in the soil, moisture content changes, soil pressure variations, and cumulative collapsibility.The final results indicate that paleosollayers hinder the collapsibility process by impeding water infiltration and preventing the transmission of deep-seated collapsibility to the surface. This leads to a positive correlation between the measured collapsibility values and the number of ancient soil layers. This study aims to provide insights into the self-weight collapsibility mechanisms in loess formations where ancient soil layers are commonly found.