Background: Oxyclozanide and Levamisole hydrochloride compounded suspensions is a kind of compound anthelmintics widely used in the treatment of Fasciola hepatica and nematodes in cattle and sheep. In order to compare the pharmacokinetic parameters between the self-develop drug and the reference listed drug in sheep of the oxyclozanide and levamisole hydrochloride compound suspension, a rapid and sensitive LC-MS/MS analytical method was established, mebendazole was used as the internal standard (IS) in positive ion mode and niclosamide was used as the internal standard (IS) in negative ion mode. The method was validated in terms of linearity, selectivity, specificity, accuracy, precision, and matrix effect, and was successfully applied to a pharmacokinetic study of oxyclozanide and levamisole hydrochloride compounded suspensions in healthy sheep. ·Results: A simple and rapid LC-MS/MS analytical method was established and validated to quantify oxyclozanide and levamisole hydrochloride levels in sheep. The main pharmacokinetic parameters, that is, the maximum plasma concentrations (Cmax), the time to maximum concentration (Tmax), area under the time curve concentration (AUClast) and Terminal half-life (T1/2): the self-developed drug and the reference listed drug of oxyclozanide were 45.54±17.58 μg/mL, 22.5±2.07 h, 1845.43±851.92 h*μg/mL, 20.58±7.97 h; 34.60±5.65 μg/mL, 15.50±3.96 h, 1285.46±225.7 h*μg/mL, 23.12±5.04 h, respectively; The self-developed drug and the reference listed drug of Levamisole hydrochloride was : 2.25±0.90 μg/mL, 0.49±0.69 h, 9.51±2.20 h*μg/mL, 4.43±1.75 h; 2.41±1.11 μg/mL, 0.81±0.66 h, 9.09±2.12 h*μg/mL, 3.16±1.05 h. No significant differences were observed among the AUClast andT1/2 for Oxyclozanide self-developed drug compare with the reference listed drug, and there was a significant difference in Cmax and Tmax (P＜0.05). There were no significant differences in Cmax, Tmax, AUClast and T1/2 between the self-developed drug of levamisole hydrochloride and the reference listed drug (P > 0.05). The relative bioavailability of oxyclozanide and levamisole hydrochloride were 143.56% and 104.62%, respectively. Conclusions: A reliable, accurate LC-MS/MS analytical method was established in our study and successful applied to study the pharmacokinetics of oxyclozanide and levamisole hydrochloride compound suspension in sheep plasma. These results will be useful for further evaluations of the pharmacokinetic properties of oxyclozanide and levamisole hydrochloride.