The PFOS（perluorooctane sultonic acid）was determined using the UPLC-MS-MS after sampling the water in order to investigate the PFOS’ pollution in Chaohu Lake. Most PFOS concentrations in Chaohu Loke ranged from (8.4±1.2) ng·L^-1 to (106±10.2) ng·L^-1. The highest one is (400±51) ng·L^-1. It was little higher compared with that in the similar aqueous. The pollution resources may be the input of industrial and the municipal waster water into the lake. The primary assessment of drinking risk indicated that it is lest risk for people’s extra exposition to the PFOS if only drinking the water. However, it may affect the birds at the top of the food-chain through the bioaccumulation.