Abstract: The sand well immersion test in the loess area is a widely used field test in the engineering community for evaluating the collapsibility of loess. It not only serves to determine the collapsibility of shallow loess strata such as ground buildings and roadbeds, but is also more suitable for determining the collapsibility of deep loess foundations. To address the challenge of accurately controlling water levels in exploratory wells during immersion testing in deep loessial sand wells, an automated multistage liquid level control device was developed. The operational status of the inductive probe in different installation modes was tested through simulation tests. A switch was introduced to realize the operational state conversion of the liquid level probe in different depths. The developed system was then applied in the immersion test of a thick, collapsible, water-sensitive loessial sand well to assess its control accuracy. Simulation results show that the designed probe mounting structure effectively maintains the inductive probe in a suspended state, ensuring proper functionality. By manipulating the control switch, water level adjustment across multiple stages was successfully achieved. Application cases show that the new device achieved stable control of water levels at different depths, with the relative deviation between the automatically controlled and target liquid level maintained within 3.00%. Comparable accuracy between manual and automated control was only observed when the manual water replenishment interval was as short as 0.1 hours. The monitoring data show that the water content of the soil near the exploratory wells with automated liquid level control has increased by 7.68% and 2.03%, respectively, compared with the initial value, while the water content of the soil near the exploratory wells with manually controlled liquid level has increased by 0.25%, further confirming that the water content of the soil near the exploratory wells with manual control has increased by 0.25%. This further demonstrates that the automated multi-stage liquid level control device effectively saturates the subsurface soil below the target depth, thereby enhancing the reliability of sand well immersion tests. This study provide a technical reference for similar tests in collapsible loess regions.