To meet the demand for low-disturbance, long-term, and continuous aquatic ecological monitoring, adsorption-mechanism-based, low-instrument-dependence passive sampling of environmental DNA (eDNA) has emerged as an important complement to active filtration. However, the effectiveness and accuracy of this method rely on eDNA enrichment on the material surface, which is jointly influenced by material properties, temperature, hydrodynamics, water chemistry, and biodegradation. Consequently, results tend to vary with environmental conditions, rendering direct comparisons across different water bodies difficult. The enrichment mechanisms and recent advances in eDNA passive sampling were reviewed. The influence of material pore structure and surface chemistry on eDNA adsorption, retention, and anti fouling performance was sorted out, and the governing patterns by which key environmental factors determined enrichment efficiency and failure operation were summarized. Building on this synthesis, pathways for optimizing adsorptive materials were proposed, including tuning surface chemical properties, enhancing adsorption through composite designs, and optimizing pore structures, as well as the potential of emerging porous materials such as metal-organic frameworks (MOFs) for in situ protection and stable enrichment. Key points for standardizing sampling were also summarizd, including selecting hydrodynamically stable and representative microenvironments, setting appropriate sampling durations, necessary spatial-temporal replicates, and concurrently recording key environmental variables (e.g., temperature, flow, and pH) to reduce site-and season-driven variability. Finally, a quantitative framework was proposed in which the accumulated signal was expressed as a net enrichment rate per unit time, enabling estimation of an approximate eDNA concentration and its uncertainty range, thereby improving the interpretability of passive-sampling results.