To investigate pharmacokinetics ofbaicalin after an oral administration of different Shuang-Huang-Lian （SHL） formulations to rats. Different SIlL formulations were orally administered to rats. The concentrations of baicalin in rat plasma were determined by HPLC, the non-compartmental pharmacokinetic parameters and population pharmacokinetic parameters of baicalin were estimated by WinNonlin and NONMEM. The plasma concentration profiles of baicalin demonstrated double-peak phenomenon except for group microemulsion prescription 2. Population pharmacokinetic model developed includes four covariates, which were the effect of formulation （FORM） on CL/F and V/F, the effect of body weight （BW） on Ka, and the effect of gender （GEND） on V/F. Numbers 1 to 6 denote SHL formulation decoction, oral liquid, colloidal solution, microemulsion prescription 1, microemulsion prescription 2 and granule, respectively. The equations for the parameters are as following： CL/F = （0.432 ＋ 0.529）. e^ηCl L/h if formulation was 2 or 6, otherwise CL/F = 0.432. e^ηCl L/h ; V/F = （11.3- 4.03 - 3.87. GEND）. e^ηv L if formulation was 5, otherwise V/F = （11.3 - 3.87. GEND）. e^ηv L ; Ka = 0.475. [1 - 0.0223. （BW - 195.1）]. e^ηKah^-1. SHL formulations have significant effects on the nharmacokinefic narameters.
