The objective of this paper is to establish the high performance liquid chromatog. method for detecting cinnarizine concentration in dog plasma, and evaluate the pharmacokinetics and the sustained-release performance of the cinnarizine floating sustained-release tablet by this method.Plasma was extracted by n-hexane-chloroform (3:2).The analyzing method included an high performance liquid chromatog. column of spherisorb ODS (150 mm × 4.6 mm, 5 μm); a mobile phase of 0.04% triethylamine NH4H2PO4 (0.01 mol/L-1, pH 4.7) in aqueous solution-acetonitrile (40:60), and a flow rate of 0.8 mL/min-1 (injection volume 20.0 μL).Results showed that the linear range of cinnarizine was 15-1500 ng/mL-1; the relative recoveries were 86.7-101.2%; the absolute recoveries were 78.5-88.9%; the intraday relative standard deviation was less than 3.26%; the intraday relative standard deviation was less than 6.38%.The main pharmacokinetic parameter, Tmax, was 3.48, 2.98, or 0.83 h, and the corresponding AUC value was 5460.67, 4019.5 or 2524.4 ng/h/mL-1 using the trapezoidal method, after taking floating sustained-release tablets, gel-matrix sustained-release tablets or conventional tablets.The bioavailability of the cinnarizine floating sustained-release tablet or the gel-matrix sustained-release tablet was 237.72% or 155.89%, resp., as compared with the conventional tablet.It was concluded that the method is sensitive, accurate and reliable in the measurements of dog pharmacokinetic study.The floating sustained-release tablet has a reliable sustained-release effect, resulting in a statistically higher bioavailability than those of the gel-matrix sustained-release tablet and the conventional tablet.