Abstract: OBJECTIVE To establish the simultaneous determination of baicalin， chlorogenic acid and forsythiaside A in rat plasma and its application to pharmacokinetic study of Shuang-huang-lian in rats.METHODS Plasma samples were prepared with methanol-ethye acetate-trifluoroacetic acid (49∶48∶3) at a flow rate of 1.0 mL/min and detected with a mobile phase of acetonitrile-water containing 0.2% formic acid using ESI with negative ionization mode. Ions monitored in SIM mode were set as m/z 353M-H^- for chlorogenic acid; m/z 445M-H^- for baicalin; m/z 623M-H^- for forsythiaside A. The concentration-time curves of baicalin， chlorogenic acid and forsythiaside A were simulated by Winnonlin5.2 and the pharmacokinetic parameters were calculated.RESULTS The calibration curve was linear within the range of 10~2 000 ng/mL for baicalin， 5~500 ng/mL for chlorogenic acid and forsythiaside A (r≥0.991). The RSDs of intra and inter day were all less than 15%， and the stability of baicalin， chlorogenic acid and forsythiaside A were controlled by the range of 90.9%~103.1%. The methods were all satisfied for the FDA level in analysis drug in vivo.CONCLUSION This method is simple， sensitive， and accurate， which can be used for analyzing Shuang-huang-lian in vivo.