Abstract: Compound nicotinic acid extended-release and simvastatin immediate-release double-layer tablets were developed and their in vitro release characteristics were evaluated.The LC-MS/MS method was established for the determination of the concentration of nicotinic acid and simvastatin in blood and investigate the pharmacokinetics and relative bioavailability in 6 Beagle dogs with the double-period and double-crossover dosage regimen.After oral administration of the test and reference tablets,c_max of nicotinic acid was (6.43±0.80) and (6.38±0.47) μg/mL; t_max was (2.80±1.00) and (2.50±1.00) h;AUC was (30.16±4.51) and (27.49±4.04) μg ·h/mL，respectively.c_max of simvastatin was (38.65±1.71) and (40.54±2.33) ng/mL; t_max was (1.50±0.40) and (1.50±0.40) h,AUC was (118.76±11.83) and (115.76±5.46) ng ·h/mL,respectively.Statistical analysis indicated that AUC,c_max and t_max of test preparations were equivalent to reference preparations.So it is bioequiavailability between the test and reference preparations in Beagle dogs.