In recent years,new psychoactive substances(NPS) are popular rapidly on the illicit drug market,which have attracted a great concern all over the world.The surge in abuse of NPS has become a serious social problem.As one of the largest growing class of NPS,synthetic cathinones have been widely abused for their cocaine and amphetamine-like pharmacological effects,and have received a widespread attention in many countries.In this article,a gas chromatography-mass spectrometry(GC-MS) with liquid-liquid extraction was developed for the simultaneous determination of eight synthetic cathinones,i.e.methcathinone(MC),4-chloroethcathinone(4 CEC),4 methylpentedrone(4-MPD),3,4-methylenedioxy-N-methylcathinone(MDMC),4′-methyl-α-pyrrolidinopropiophenone(4-MePPP),3,4-methylenedioxy-N-ethylcathinone(MDEC),4′-chloro-α-pyrrolidinopropiophenone(4-Cl-α-PPP) and 3,4-methylenedioxypyrovalerone(MDPV).Firstly,the extraction factors influencing the extraction efficiency were investigated,and the optimal procedures of liquid-liquid extraction were as follows:500 mL blank urine was added with 5 μL internal standard N,N dimethylaniline standard solution(1.00 mg/mL),0.50 mL Na2CO3-NaHCO3 buffer solution(pH 10.80),50 mg sodium chloride and 0.5 mL cyclohexane were vortex-oscillated for 3 min,and then centrifuged at 5 000 r/min for 10 min,the supernatant was injected and analyzed on GC-MS spectrometer.Secondly,the instrumental conditions for GC-MS including GC and MS parameters for simultaneously determining eight synthetic cathinones were optimized in details,and then the qualitative and quantitative analysis of these target compounds in urine were performed by GC-MS,the characteristic ions for qualitative and quantitative analysis were both obtained while the GC-MS spectra were recorded at the same time,then the regression equations,limits of detection(LODs),limits of quantitation(LOQs),inter day and intra day precisions and average recoveries for eight synthetic cathinones in urine were examined,respectively.Experimental results showed that the analytical approach developed was sensitive in qualitative analysis and accurate in quantitative analysis of synthetic cathinones in urine.MC,4 CEC,MDMC and MDEC exhibited good linearity in the concentration range of 0.02-5.00 μg/mL with their LODs and LOQs of 0.01 μg/mL and 0.02 μg/mL,respectively.Their recoveries ranged from 93.2% to 98.5% with the intra day precision and inter day precision not more than 7.8% and 8.8%,respectively.4-MPD,4-MePPP and 4-Cl-α-PPP exhibited good linearity in the concentration range of 0.01-5.00 μg/mL with their LODs and LOQs of 0.005 μg/mL and 0.01 μg/mL,respectively.Their recoveries ranged from 93.6% to 994% with the intra day precision and inter day precision not more than 60% and 7.4%,respectively.MDPV exhibited good linearity in the concentration range of 0.005-5.00 μg/mL with its LODs and LOQs of 0.002 μg/mL and 0.005 μg/mL,respectively,Its recoveries ranged from 92.4% to 97.2% with the intra day precision and inter day precision not more than 4.4% and 53%,respectively.Therefore,the developed method could not only offer a certain scientific and technical support for the relevant material evidence identification and litigation cases,but also provide a tool to combat drug crime in our country.