A rapid, specific and sensitive method was developed for the simultaneous determination of eight Aconitum alkaloids: aconitine (AC), mesaconitine (MA), hypaconitine (HA), benzoylaconine (BAC), benzoylmesaconine (BMA), benzoylhypaconine (BHA), aconine and mesaconine in rat blood by ultra-performance liquid chromatography coupled tandem mass spectrometry (UPLC-MS/MS). The UPLC-MS/MS system coupled with an electrospray ionization (ESI) source was operated in a positive mode via multiple-reaction monitoring (MRM). Samples were treated with methanol to remove protein prior to analysis by UPLC-MS/MS. The analytes were separated with a Waters C18 column (1.7 µm, 50 × 2.1 mm) and a gradient elution using acetonitrile and 0.1% formic acid-water as the mobile phases. The linear response range was from 0.125 to 1000 nmol/L for these eight alkaloids and the correlation coefficients (r(2) values) were all higher than 0.997. The method was validated with respect to precision, accuracy, recovery, matrix effect, carryover effect and sample stability, and found to be within the acceptable limits. The developed and validated method was successfully applied to simultaneously determine the eight Aconitum alkaloids in rats blood after intravenous administration of a mixture of AC, MA and HA.