OBJECTIVE：To establish a method for the determination of aloesin in plasma of rats ，and to investigate pharmacokinetic characteristics of aloesin. METHODS ：The plasma samples were precipitated with methanol. Using aloeresin D as internal standard ，the plasma concentration of aloesin was determined by LC-MS/MS. The determination was performed on Synergi Hydro-RP column with mobile phase consisted of 0.1‰ formic acid-methanol （gradient elution ）at the flow rate of 0.50 mL/min. The column temperature was 30 ℃，and sample size was 5 µL. The electrospray ionization source was applied to carry out negative ion detection with multiple reaction monitoring mode . The ion transitions for quantitative analysis were m/z 393.1→272.9（aloesin） and m/z 555.3→144.9（internal standard ），respectively. The concentration of aloesin in venous blood was determined by above method at 0.083，0.167，0.333，0.667，1，1.5，2.5，4，6，8，10 h after intravenous injection （3.35 mg/kg）and intragastric administration（16.75 mg/kg）of aloesin. DAS 3.0 software was used to calculate pharmacokinetic parameters. RESULTS ：The linear range of aloesin were 1-600 ng/mL（r＝0.994 5）. The lower limit of quantification was 1 ng/mL，and RSDs of within and between batches were less than 15％；accuracies within and between batches were within ±15％. The matrix factors were （92.74± 4.33）％-（94.84±2.57）％，and extraction recoveries were （69.04±2.13）％-（75.03±2.84）％；the deviation between the measured results of the stability test and the theoretical values were within ±15％. After intravenous injection and intragastric administration of aloesin ，main pharmacokinetic parameters were as follows ：cmax were（10 693.3±2 745.3）and（223.3±36.2）ng/mL；t1/2 were （2.45±1.45）and（3.33±1.91）h；AUC0－24h were（4 190.6±883.6）and（1 210.1±93.9）ng·h/mL（n＝3）. Absolute bioavailabi- lity was 11.13％. CONCLUSIONS ：The established method is rapid and sensitive for plasma determination of aloesin ，and suitable for its pharmacokinetic study.