At water temperature of (25±1) ℃, Carassius auratus was treated by oral administration of diclazuril in dose of 3 mg/kg once a day for 5 d. The concentration of diclazuril in the plasma and muscle of Carassius auratus at 0.5, 1, 1.5, 2, 3, 5, 7, 10, 12, 15, 18, 24, 36, 48, 72, 120, 240, 360, 480, 720, 1 080, 1 440, 2 160, 2 880 and 3 600 h after feeding were determined by high performance liquid chromatography, and the pharmacokinetics of diclazuril in Carassius auratus were studied．The results showed that following oral administration, the plasma and muscle concentration-time course of diclazuril both conformed to a two-compartment open model with the first order absorption. The pharmacokinetic equations were as follows, Cplasma=9.89e-6.710E-3t+3.66e-9.04E-4t -0.74e-4.379t, Cmuscle=1.026e-6.379E-2t+0.1001e-1.53E-2t-1.82e-5.566t. The time to peak (Tmax) of diclazuril in plasma and muscle were 11.11 and 11.00 h, respectively, and the peak concentration (Cmax) were 30.58 and 1.108 mg/L, respectively, and the area under the concentration-time curve (AUC) were 16 783 and 20.05 mg/(L·h ), respectively, and the elimination half-life（T1/2β）were 827.6 and 45.41 h, respectively.The results showed that diclazuril was eliminated slowly from Carassius auratus. This study provided theoretical basis for the actual breeding of Carassius auratus with diclazuril, and  technical support for the determination of residues and pharmacokinetic study of diclazuril in the other aquatic products.