Abstract: To investigate the effect of combination of schisandrin B and doxorubicin on the pharmacokinetic behavior of doxorubicin in SD rats. An LC-MS/MS method was established for the determination of doxorubicin and its main metabolite doxorubicinol in SD rats plasma. Separation was performed on Agilent Eclipse XDB-C₁₈ column(100 mm×2. 1 mm, 3. 5 μm)using 0. 1% formic acid solution and acetonitrile as mobile phase with a liner gradient program. The ion transitions were performed under ESI position model at m/z 544. 2→397. 3(doxorubicin), m/z 546. 2→399. 2(doxorubicinol), m/z 528. 2→381. 2(daunorubicin, internal standard). Calibration curves of doxorubicin(0. 500-500 ng/mL)and doxorubicinol(0. 200-50. 0 ng/mL)showed good linear regression. The precision and accuracy met the requirements. The variation coefficient of extraction recovery and matrix effect was less than 15%. The AUC_0-t of doxorubicin were(605. 69±145. 84)and(564. 53±23. 99)ng ·h/mL in alone and combined group, respectively. The AUC_0-t of doxorubicinol were(26. 69±13. 41)and(29. 00±2. 78)ng ·h/mL, respectively. Results indicated that, schisandrin B had not affected the pharmacokinetic behavior of doxorubicin in SD rats.