A sensitive mass spectrometric approach was developed for the detection of trace lead in water.The microwave plasma torch(MPT) was used as the ion source for direct analysis of water samples without any pretreatments.Aqueous samples were introduced in the plasma through the central cube of the MPT after nebulization and dying,the generated ions were detected by a homemade quadrupole mass spectrometer(Q-MS).The quantitative results showed that the limit of detection(LOD) was at the level of 20 ng/L,and the linear range was 200-1 000 ng/L with RSD of 5.3%.These quantitative indexes were better than the results from the international commercial linear ion trap mass spectrometer(LTQ-MS) under the same MPT working conditions.However,the characteristical mass spectra obtained on MPT-Q-MS were simpler and easier to be assigned without further MSn experiments,thus MPT coupled with Q-MS will be suitable for the development of the portable analysis instrument,and have the potential applications in environmental controlling and drinking water detection.