A new ionization mass spectrometry method was established for the detection of trace cadmium in water.Microwave plasma torch(MPT) as the ion source,combined with a mass spectrometer can be directly used to analyze water samples without any sample pretreatment.Water sample was transformed into aerosol by directly atomizing nebulizer.The aerosol after heating-cooling cycles and drying of concentrated sulfuric acid,was introduced into the plasma through the MPT central conduit,generating ions detected with quadrupole mass spectrometer(QMS) to afford cadmium MPT features MS.Quantitative analysis was carried out based on the characteristics of cadmium mass.The results showed that the signal intensity 114Cd had a good linearity with the solution of cadmium ion concentration within 300-3 000 ng/L with a correlation coefficient of 0.994 96,the detection limit(LOD) was 72.7 ng/L.Actual water samples(tap water,Tai Hu Lake water,Gan Zhou Long Nan well water,mineral water) were analyzed.The recoveries ranged from 90.6%to 112.2%with relative standard deviations(RSDs,n=10) of 7.1%-21.5%.The detection for a single sample could be completed within 2-3 min.Therefore,as a powerful complement to traditional ICP mass spectrometer,the fast MPT mass spectrometry dection of hazardous metals cadmium in water has certain advantages,and could be developed as a line analysis method for environmental water,tap water quality monitoring,etc.