The concentration of PAHs in the water source area of the Taihu Basin was monitored and analyzed using GC-MS. The results show that the concentrations of PAHs in the water phase, suspended particular matter, and sediments in March were 63. 5 to 393. 9 ng/L, 167 to 4 358. 2 ng/g, and 940. 8 to 7398. 3 ng/g, respectively, being higher than the values in June, which were 21. 1 to 64. 6 ng/L, 125. 6 to 282. 3 ng/g, and 337. 3 to 1 318 ng/g, respectively. The concentration of monomer PAH varied significantly in different months, and could be controlled by the diversities of the pollution sources, flow dilution, and hydrodynamic conditions. The characteristics ratio suggested that the PAHs in the water phase and suspended particular matter mainly came from the oil leaks and burning in June, while the PAHs in sediments in March and June had the mixing source. The ecological risk assessment shows that the ecological risks of PAHs in the water phase, suspended particular matter, and sediments were relatively small, while the concentration of monomer PAH at some sampling sites was higher than ER-L and SQV-L(low value of risk assessment)based on iological impact test, indicating certain health risks.