An ultra high performance liquid chromatography-quadrupole-time of flight mass spectrometry(UHPLC-QTOF MS/MS) was established for the simultaneous determination of 4 kinds of new psychoactive substances of cathinone in blood samples,including 1-(3,4-methylenedioxyphenyl)-2-methylaminopropan-1-one(methylone),1-(3,4-methylenedioxyphenyl)-2 ethylaminopropan 1-one(ethylone),1-(4-chlorophenyl)-2-methylaminopropan-1-one(4 CMC) and 1-(4-chlorophenyl)-2-ethylaminopropan-1-one(4-CEC).0.5 mL blood sample was mixed with water and acetonitrile by a volume ratio of 5∶2∶13,vortex oscillated for 1 min,and centrifuged at 12 000 r/min for 15 min to precipitate the protein.The supernatant was separated on an Acquity UPLC-BEH C18 column(2.1 mm×100 mm,1.7 μm),with 0.1% formic acid-water(5 mmol/L ammonium acetate) and acetonitrile as mobile phases by gradient elution,and detected in positive ion［M+H］+ scanning under multiple reaction monitoring(MRM) mode.Results showed that there were good linear relationships for four target drugs in the concentration range of 5-500 ng/mL,with the limits of detection and limits of quantitation of 2 ng/mL and 5 ng/mL,respectively.The recoveries ranged from 87.3% to 111% with the intra day precision and inter day precision not more than 8.1% and 8.6%,respectively.The method could be used for the simultaneous detection of 4 new psychoactive substances of cathinone in blood samples to meet the needs of actual inspection work.