<p>Conventional methods for treating potato starch processing wastewater (PSPW) are challenged by issues such as poor adaptability and high idle rates. Returning wastewater to the field, as a resource utilization strategy aimed at reducing pollutants and recovering nutrients, has emerged as a preferred approach for PSPW treatment. However, the unclear safe carrying capacity of soil in this process poses potential ecological risks. To scientifically evaluate the impact of repeated PSPW irrigation on soil safety performance, this study employed a soil infiltration system (SIS) to simulate the wastewater infiltration process. The results demonstrated that the SIS achieved average removal rates of 74.38%, 59.68%, 45.10%, and 77.94% for chemical oxygen demand (COD_Cr), total nitrogen (TN), ammonia nitrogen (NH₄⁺-N), and total phosphorus (TP), respectively. Furthermore, multiple PSPW infiltrations led to weakly alkaline soil conditions and significant accumulation of organic matter, nitrogen, and phosphorus in the topsoil. Concurrently, the infiltration process altered the microbial community structure and reduced microbial diversity in the surface soil. The composition and function of the microbial community varied significantly with soil depth, with the community in the subsoil resembling that in the original, untreated soil. This study elucidates the patterns of pollutant removal during PSPW infiltration, the response of soil physicochemical properties, and the changes in microbial community structure at different soil depths. It provides a scientific basis for assessing the ecological impact of PSPW re-irrigation on soil and supports the potato industry in Northwest China in achieving green development goals.</p>