Abstract: OBJECTIVE To establish an HPLC-MS/MS method for simultaneous determination of aristolochic acid I, aristolochic acid II and aristolactam I in Houttuynia cordata and Compound Yuxincao mixture.METHODS Phenomenex Kinetex C₁₈(100 mm×2.1 mm, 2.6 μm) column was used for separation. The mobile phase consisted of acetonitrile and 0.2% formic acid solution with gradient elution. The flow rate was 0.3 mL·min^-1and the column temperature was 30℃. Electrospray positive ion source was used for mass spectrometry detection by multiple reaction monitoring mode. RESULTS The liner range of calibration curve was 11.91-1 985 ng·mL^-1(r=0.995 3), 16.87-2 812 ng·mL^-1(r=0.995 7) and 3.404-567.4 ng·mL^-1(r=0.996 6) for aristolochic acid I, aristolochic acid II and aristolactam I. The average recoveries of each component was in the range of 85%-111%, RSD was 0.2%-6.7%. The limit of detection and quantitation for aristolochic acid I were 2.395 ng·mL^-1 and 7.984 ng·mL^-1, for aristolochic acid II were 3.389 ng·mL^-1 and 10.50 ng·mL^-1, and for aristolactam I were 0.334 2 ng·mL^-1 and 1.113 ng·mL^-1. CONCLUSION The method has good sprcificity, sensitivity and accuracy, and it is suitable for the content determination of aristolochic acid I, aristolochic acicl II and aristolactam I in Compound Yuxincao mixture.