According to the pollution characteristics of the coal mine and coal gangue hillock, 16 kinds of polycyclic aromatic hydrocarbon (PAHs) registered by EPA in subsidence water samples around coal gangue hillock were selected and detected by high performance liquid chromatography (HPLC). Distribution of single PAH and total PAHs and composition of rings number of PAHs were analyzed. Ecological risk assessment of such water body was carried on by risk quotient method and the results showed that unsuitable development of such water body may cause harm to human.