The vertical distributions of 16 polycyclic aromatic hydrocarbons (PAHs) were investigated from a sediment core in the Lake Bosten, Xinjiang. Meanwhile, the possible source and risk assessment of PAHs in Lake Bosten were also discussed. The total PAHs concentration in the sediment core ranged from 37.5 ng x g(-1) to 184.5 ng x g(-1), and Naphthalene and Phenanthrene were the dominant compounds throughout the core. Over the one hundred year, the vertical profile of PAHs underwent significant changes around 1950s. The vertical distributions of PAHs had little change and low molecular weight PAHs were dominant PAHs before 1950s. Since then, the high molecular weight PAHs appeared and increased with fluctuations. A sharp increase in PAHs level and individuals was observed especially after 1990s and a maximum was found in the surface sediment. The results suggested PAHs in Lake Bosten were from the local sources, which were dominated by the low temperature combustion. Besides, the abundance of PAHs from high temperature combustion processes, such as combustion of industrial coal and vehicle emission, increased significantly in recent years. However, based on the results of risk assessment, the PAHs may not induce adverse biological effects on the aquatic ecosystem in Lake Bosten.