Referring to the 96 h-LC₅₀ values of Perfluorooctane sulfonate (PFOS) on Danio rerio, four groups with concentration of 0, 1, 5 and 10 mg/L were set to explore the toxic effect of PFOSon fish. Indices of the physiological and biochemical parameters, such as the activities of alkaline phosphatase(ALP), lactate dehydrogenase(LDH), and acetylcholinesterase (AchE) in the fish head, the superoxide dismutase(SOD), catalase(CAT), malondialdehyde (MDA) and ALP in the fish visceral were analyzed. ALP, SOD and MDA in the muscle of Danio rerio were also determined. The results showed that the activities of ALP and AchE in the head would be inhibited at the beginning of the experiment, then recover gradually. PFOS with medium-low concentration(1mg/L and 5 mg/L)induced LDH activity in the head to rise remarkably. ALP in the visceral mass was significantly induced and showed dose-effect relationship with PFOS concentration. After being significantly induced at 0.5-1 h, the activity of SOD and CAT declined later, but no significant inhibition was found. The content of MDA was significantly induced. In the muscle, the activity of ALP was significantly inhibited by PFOS(P < 0.05), but SOD activity and MDA content were not affected.