OBJECTIVE： To establish a method for the determination of emodin， rhein and calycosin in rat plasma， and to study pharmacokinetics of Qixue extract in rats. METHODS： LC-MS/MS method was adopted. The determination was performed on Thermo C18 column with mobile phase consisted of acetonitrile-0.1％ formic acid solution （gradient elution）， and flow rate of 0.2 mL/min. The column temperature was set at 30 ℃， and sample size was 20 μL. The quantitative ions were emodin m/z 269.7→226.1， rhein m/z 283.7→239.9， calycosin m/z 283.5→268.5 and diazepam m/z 285.0→154.1. The blood concentration of samples from orbital cavity of 6 rats were determined 0.08， 0.17， 0.25， 0.5， 0.75， 1， 2， 4， 6， 8， 12 h after intragastric administration of Qixue extract 8.91 g/kg （by clinical dosage）. DAS 1.0 pharmacokinetic software was employed to calculate pharmacokinetic parameters. RESULTS： The linear ranges of emodin， rhein and calycosin were 1.988-198.8 ng/mL （r＝0.998 8）， 2-200 ng/mL （r＝0.998 8） and 2.092-209.2 ng/mL（r＝0.998 5）， respectively. RSDs of precision and accuracy tests were all less than 7.78％ （n＝5）. The recoveries were 92.13％-102.23％， 90.15％-93.67％ and 90.33％-104.63％ （n＝5）， respectively. RSDs of stability tests were all less than 6.54％ （n＝3）. The pharmacokinetic parameters of emodin， rhein and calycosin were as follows as t1/2 were （1.95±0.53）， （3.55±1.25）， （4.21±1.14） h； AUC0-12 h were （192.67±40.58）， （93.67±20.26）， （608.41±108.36） μg·h/L； cmax were （89.56±12.87）， （31.84±10.58）， （300.56±50.57） μg/L； tmax were （0.50±0.00），（0.75±0.23），（1.00±0.00） h； CL were （5.45±1.12）， （2.09±0.47）， （10.01±1.25） L/（h·kg） （n＝6）， respectively. CONCLUSIONS： Established method is highly sensitive， accurate and reliable. The elimination process of emodin， rhein and calycosin are first-order elimination， which is in line with two-compartment model.