We collected 74 water samples from 37 sites along the Ganjiang River and its tributaries in January and July, 2015 to analyze the spatial distribution of dissolved metals (Be, Al, V, Mn, Fe, Co, Ni, Cu, As, Mo, Cd, Sb, Tl, Pb and U), and to estimate the contributions of pollution sources in Lake Poyang Basin. The results showed that the concentrations of dissolved metals in most water samples met the national water quality standards, and Fe is the primary trace metal beyond the national standard, i.e. 21.60% of water samples had higher Fe concentrations than the national drinking water quality standard, followed by As (8.10%), Mn (4.05%), Tl (4.05%) and Al (1.35%). In addition, the concentrations of Be, Al, V, Fe, Co, Ni, Cu and U during the dry season were significantly higher than those during the wet season, while others had no significant difference. Based on the spatial distribution of dissolved metals, three spatial regions were identified:C1 (Xiangshui River Basin, Zhangshui River Basin and Ganzhou section of Ganjiang River), C2 (Taojiang River Basin, Yuanshui River Basin and Jinjiang River Basin), and C3 (the other regions beyond C1 and C2). The contamination order in the three regions was C1 > C2 > C3. The highest concentrations of Be, Al, Cu, Mo, Sb and As occurred in C1; while V, Mn, Fe, Ni and Cd in C2. The primary sources of dissolved metals in the Ganjiang River were mining waste water, leaching water of slag and agricultural soils, and steel industry waste water. We estimated that more than 40% of Be, Al, Cu, Pb and U were from mining waste water, more than 35% of Cu, As, Mo and Cd from leaching water of slag and agricultural soils, and more than 41% of V, Mn, Co and Ni from the steel industry waste water.