Abstract: The treated Aconitum brachypodum Diels powder sample(0.1 g) was taken, and extracted ultrasonically in 5 mL of 80% (volume fraction) methanol solution at 25 ℃ for 20 min. The supernatant was passed through a 0.22 μm filter membrane to obtain the test solution Ⅰ, which was used for determination of mesaconitine, hypaconitine, benzoylhypaconine, and benzoylmesaconine. An appropriate amount of the test solution Ⅰ was taken and diluted 100 times with 50% (volume fraction, the same below) methanol solution to obtain the test solution Ⅱ, which was used for determination of bullatine B. An appropriate amount of the test solution Ⅱ was taken and diluted 10 times with 50% methanol solution to obtain the test solution Ⅲ, which was used for determination of aconitine and benzoylaconine. Acquity UPLC BEH C₁₈ column was used as the stationary phase, and a mixture of 0.1% (volume fraction) formic acid solution and acetonitrile at different volume ratios was used as the mobile phase for gradient elution. The multiple reaction monitoring mode was carried out by the electrospray ion source under positive ion mode in mass spectrometry analysis. As shown by the results, linear relationships between the corresponding peak areas and mass concentrations of 7 alkaloid compounds were found in the range of 1.0-100.0 μg·L⁻¹, with detection limits (3S/N) of 0.002 1-0.019 5 μg·L⁻¹. RSDs (n=6) of the determined values in the instrument precision, repeatability, and stability tests were less than 5.0%. Test for recovery was made by the standard addition method, giving results in the range of 94.5%-105%. This method was used for analysis of 12 batches of Aconitum brachypodum Diels samples. The contents of aconitine, benzoylaconine, and bullatine B were higher, and the contents of the other four alkaloid compounds were relatively lower.