Abstract: The study explores the effect of Fenpropathrin on the acute toxicity and Na+-K+-ATPase activity, histopathological changes of carp (Cyprinus carpio) gills. According to the acute toxicity result, the 96 hour lethal concentration (96 h LC50) is 8.53 gL-1 and the safe concentration (SC) is 0.853 gL-1. Exposed to Fenpropathrin at concentrations of 0, 0.43 gL-1, 0.85gL-1, 1.70gL-1 and 4.27 gL-1, the gill tissue of carp were collected at the 1st, 3rd, 7th, 14th, 21st day, respectively. Results indicate that the activities of Na+/K+-ATP enzyme in gill tissue during different exposure periods vary in a wave shape, i.e. first decrease, then increase, and decrease again as the exposing time progresses at the same concentration. The ATPase activities reach the lowest at 3rd day, which are very significantly different from the control (P0.01), with inhibition rates of 42.49%, 27.48%, 59.03% and 46.31%, respectively. The enzyme activities of all concentration groups reach the highest at14th day, which are significantly (P0.05) or very significantly (P0.01) higher than that of the control. At 21st day, the enzyme activities of the highest concentration group are significantly lower than that of the control except the other 3 concentration groups. The HE staining histological changes in the gills include gill-amells distortion, epithelial cell and pillar cell shedding, blood capillary of gill-amells expanding and hyperaemia, mucilage cell and basal cell hyperplasia, sometimes even gill-amells adhesion and gill filament becoming club-shape. The damages of gill are related to concentration and effect of time accumulation.