Abstract: The study reveals the characteristics of spatial and temporal variations in the ecological risk of aquatic organisms for ammonia nitrogen in the Yellow River Basin, which is of great significance for the control of ammonia nitrogen risk and water ecological environmental protection in the Yellow River Basin, as well as the refinement and revision of the Water Environmental Quality Standard for ammonia nitrogen. Based on the " China National Aquatic Life Criteria for Ammonia " issued by the Ministry of Ecology and Environment, this paper applied statistical methods and risk quotient method to study the spatial and temporal variation characteristics of ammonia nitrogen risk in the Yellow River Basin in 2022 and identify the key periods and areas of concern. A methodology for comparing the spatial and temporal variability of ammonia nitrogen risk was established through the coefficient of variation, and the main influencing factors of ammonia nitrogen risk in the Yellow River Basin were identified using Spearman correlation analysis. The results showed that: (1) The spatial variability of long-term toxicity criteria and risk quotients of ammonia nitrogen in the Yellow River Basin was 3.3 and 2.1 times higher than the temporal variability, respectively. (2) Temporally, the concentration of ammonia nitrogen and the risk quotient increased significantly in winter, with the proportion of risky sections increasing from 2.3% in spring to 13.6% in winter, and the winter situation required urgent additional attention. (3) Spatially, 91% of the sections in the Yellow River basin have no or low risk of ammonia nitrogen, but the problem of long-term toxicity risk of ammonia nitrogen is more prominent in some sections of the Yellow River tributaries, such as the Wei River and the Fen River, especially the confluent sections. (4) The risk of ammonia nitrogen in the Yellow River basin was mainly affected by the pH of the water body in addition to the ammonia nitrogen concentration, while the impact of water temperature on ammonia nitrogen risk was relatively small. The study indicated that it is more important to develop regional water quality standards and discharge standards for ammonia nitrogen than seasonal differentiation standards, and it is necessary to pay extra attention to the tributaries and the main tributary confluence sections as well as to establish water quality monitoring and warning mechanisms. In addition to controlling the discharge of ammonia pollutants, attention should be focused on water bodies with high pH.