Landscape pattern is a significant indicator for representing the spatial distribution characteristics of land use and land cover change (LUCC). The landscape pattern changes caused by human activities are important factors that alter the hydrological processes within a watershed. Existing studies on the impact of landscape patterns on runoff-sediment processes only rely on single-source LUCC data, neglecting the uncertainty brought by LUCC data. In this study, the Hushan watershed in the Poyang Lake region was selected as the study area. Based on rainfall, runoff, and sediment data from 1963 to 2022, combined with seven periods of LUCC data from 1990 to 2020 at the same resolution obtained from three LUCC products, the characteristics of rainfall, runoff, sediment, and land use changes in the watershed were analyzed. Correlation analysis and partial least squares regression (PLSR) were used to investigate the impact of landscape pattern changes on runoff-sediment process characteristics and their uncertainty. The results showed that from 1963 to 2022, the annual sediment transport modulus (STM) and suspended sediment concentration (SSC) in the Hushan watershed showed a significant increasing trend (P < 0.001), while the Runoff Depth (RD) showed an insignificant increasing trend. The main LUCC types in the watershed were forest land and cultivated land, accounting for approximately (79.57±6.03)% and (15.72±2.36)% of the watershed area, respectively. From 1990 to 2020, urban expansion mainly encroached on forest land and cultivated land, with significant land conversions between the two. There were significant differences in landscape pattern characteristics among different LUCC types (P < 0.05), mainly due to the identification differences of shrub land and grass land by different LUCC products. In general, the maximum patch area of the landscape in the study area decreased, landscape fragmentation increased slightly, and landscape diversity increased to some extent. The influence of landscape patterns obtained under different LUCC products on runoff and sediment varies. The consistent findings across all products indicated that Patch Density (PD) and Contagion Index (CONTAG) are negatively correlated with RD, STM, and SSC, while Edge Density (ED), Shannon Diversity index (SHDI), and Shannon Evenness Index (SHEI) are positively correlated with STM and SSC. The PLSR model indicates that the proportion of the Largest Patch Index (LPI), Patch Cohesion (COHESION), Landscape Division (DIVISION), SHDI, and Modified Simpson Evenness Index (MSIEI) play significant roles in the variations of RD, STM, and SSC. Using ED to represent area-edge characteristics, PD and CONTAG to represent aggregation-dispersion characteristics, and SHDI and SHEI to represent diversity characteristics can relatively reduce the uncertainties caused by LUCC products in research results. By increasing the connectivity between forest land and cultivated land, reducing scattered cultivated land, and avoiding mutual conversions between the two landscape types as much as possible, the degree of landscape fragmentation can be reduced, and soil erosion in the watershed can be alleviated. The findings of this study provide a reference for soil erosion control and ecological civilization construction in the Poyang Lake region.