Abstract: In order to understand the heavy metal pollution status of Chishui River, water samples were collected from 31 sections of the main stream and major tributaries in August 2023 (wet season) and April 2024 (normal season).The spatiotemporal distribution of the heavy metals were analyzed based on measured values of nine heavy metals, namely, Cr, Mn, Fe, Cu, Zn, As, Cd, Pb and Hg.The results showed that the concentrations of Cr, Mn, Fe, Cu, Zn, As, Cd and Pb, in different sections of Chishui River during both the wet season and normal season were significantly lower than the Class I standard of the Environmental Quality Standard for Surface Waters (GB 3838-2002) as well as the limits of the supplementary standard.However, the concentrations of Hg in each section exceeded the Class III standard.The spatial and temporal variations of heavy metal concentrations showed significant differences.Temporally, most heavy metal concentrations in the entire basin, source, upstream and midstream of the river during the wet season were higher than those in the normal season (P < 005).Spatially, the maximum concentrations of most heavy metals in the wet season (Cr, Cu, Zn, Cd, Pb, Hg, and Mn) and in the normal season (Zn, Cd, Pb, and Hg) were primarily concentrated in the middle reaches of the watershed.There were no significant differences (P > 005) in the concentrations of most heavy metals (Fe, Cu, Zn, As, Cd, Pb, and Hg) among different river sections during the same season.The evaluation of Nemero Composite Pollution Index (PN) showed that the PN values ranged from 7963 to 27301 during the wet season, indicating that each section was at a severe pollution level.During the normal water season, the PN ranged from 1598 to 21273, indicating that different sections were at the levels of mild to severe pollution.The PN values of the entire basin during the wet season were significantly higher than those in the normal season (P < 005).The maximum value of PN was observed at the section of Hushi Town during the wet season and at Datong Town during normal season.The results of this study provided scientific basis for the water environment management and pollution control of Chishui River