Abstract: A method of high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was established for the detection of methcathinone and its metabolite cathinone. Methcathinone was administered to rabbits by intravenous injection and gavage respectively. The blood of poisoned rabbits was collected at 1, 2, 4, 6 and 8 h after the administration. Then, the blood samples were extracted by internal standard proadifen hydrochloride (SKF_525A) acetonitrile solution, and the extract was filtered with 0.22 μm organic filter membrane and detected by HPLC-MS/MS. The Column Eclipse Plus C18 chromatographic column (100 mm×3 mm×1.8 μm) was adopted and the column temperature was 45 ℃, mobile phase was 0.1% formic acid aqueous solution and acetonitrile. The results of the rabbit experiment showed that after intravenous injection and gavage of methcathinone, the blood levels of methcathinone and its metabolite cathinone reached the peak within 1 h, and then gradually decreased. The peak value of methcathinone in the blood of intravenous administration was much higher than that of intragastric administration, while the peak value of metabolite cathinone was not significantly affected by the administration method. In addition, the elimination rate of methcathinone and its metabolite in blood of intravenous administration was significantly higher than that of gavage administration, and the content of methcathinone in blood 8 h after intravenous administration was lower than the detection limit. The linear relationship of methcathinone was good in the range of 0.2-2 000 μg/L, and the linear equation was y=0.014 1x+0.140 6 (r=0.999). The detection limit was 0.1 μg/L, the average recovery was 90.5%-98.5% in the concentration range of 0.5-500 μg/L. The intra-day RSD was 5.9%-7.9% and the inter-day RSD was 6.6%-8.8%. The linear relationship of cathinone was good in the range of 0.5-2 000 μg/L, and the linear equation was y=0.007 1x-0.023 1 (r=0.999), the detection limit was 0.2 μg/L, the average recovery was 90.2%-97.6% in the concentration range of 0.5-500 μg/L. The intra-day RSD was 5.7%-8.2% and the inter day RSD was 6.5%-9.1%. The method is simple and sensitive, and can be used to detect methoxyketone and its metabolite in blood samples.