Abstract: Water quality is sensitive to the changes in land use and landscape patterns. To explore the relationship between landscape patterns and water quality at different scales, Changtan Reservoir watershed was chosen as the research object. Based on 2021 water quality monitoring data, buffer zones were divided at intervals of 100m for each inlet tributary. The landscape characteristics of seven strip-shaped buffer zones ranging from 50 to 650m were calculated. Pearman correlation analysis and redundancy analysis were used to study the response relationship between water quality and landscape patterns. The results showed that: (1) The watershed of the reservoir was primarily composed of forest land, followed by arable land and water bodies. The proportion of forest land area increased with the buffer radius, while the proportion of arable land and construction land areas decreased. (2) Arable land, construction land, Contagion Index (CONTAG), and Shannon Diversity Index (SHDI) were positively correlated with water quality indicators, with arable land being a significant source of water pollution in the reservoir area. (3) The explanatory power of landscape pattern on water quality was highest at a 250m radius. Within this range, the landscape fragmentation was high, and the human activities were intense. It is recommended to strictly control farming practices within 250 meters of each tributary. Approaches including the establishment of riparian buffers and the construction of pre-reservoirs should be implemented to enhance the interception of pollutants, and to protect the water environment safety of the Changtan Reservoir watershed.