A method using reversed phase high performance liquid chromatography with UV detection has been developed for the determination of ivermectin residues in crucian blood,muscle,hepatopancreas,kidney and gonad tissues.Homogenized crucian tissues were extracted with ethylacetate prior to centrifugation.The supernatants were evaporated to dryness at 45 ℃ with nitrogen.The residues were dissolved with the mixture of methanolwater(4∶1,V/V)and defatted with hexane.After centrifugation,the underlayers were filtrated with 0.22 μm filter and then 20 μL filtrates were detected by reverse phase high performance liquid chromatography with 245 nm detection wavelength.Its method detection limit was 7.5 μg/L and 7.0 μg/kg in plasma and muscle respectively.The good linear range was 0.025-1.00 mg/kg in crucian muscle,hepatopancreas,kidney,gonad tissues and 0.025-1.00 mg/L in plasma.In different tissues,the average withinbatch and the betweenbatch standard deviations of this method are(2.55±1.78)%-(3.99±1.55)% and(4.18±3.97)%-(6.01±2.54)% respectively,with an average recovery of(90.09±6.54)%-(97.77±5.91)%.After a single oral administration of 0.4 mg/kg body weight,we detected ivermectin residues in crucian muscle tissues with this method.When the water temperature is 25 ℃,we found that the freedrug period of crucian muscle tissues should not be less than 15 days.