A rapid method for determination of poison in human blood by supercritical fluid extraction(SFE)-Supercritical Fluid Chromatograph(SFC)-tandem mass spectrometry was build.The simple pretreatment method as following: the blood sample was dropped 20 μL to a Dry Blood Spot(DBS)card,then holed 3 mm internal diameter dry blood spot,and put it into the SFE vessel to analysis by Shimadzu online SFE-SFC-MS system.Some of SFE conditions,like SFE pressure,modifier solution,and SFE temperature were investigated.By the suitable SFE condition,the linearity,limit of detection,recovery and repeatability were also studied.The results showed that the linear ranges for six benzodiazepine medicines were 1~1000 ng/mL,the percent recovery of medicines were between 80~110%and the limit of detections for most medicines in specimens were between 1~10 ng/mL.The entire method is simplified,fast,accurate,highly sensitive,and is a new method for determination of components and selected metabolites of benzodiazepine medicines in human blood.