Abstract: Lead is a toxic heavy metal with widespread industrial using. The pollution of water resources caused by lead emissions has been highly concerned for a long time. Monitoring the concentration of lead in drinking water is of great significance for preventing its deleterious effects on human health. The main methods for determination of lead in water include graphite furnace atomic absorption spectrometry (GFAAS), flame atomic absorption spectrometry (FAAS), atomic fluorescence spectrometry (AFS), inductively coupled plasma mass spectrometry (ICP-MS), anodic stripping voltammetry (ASV), dithizone spectrophotometry and so on. These methods generally need cumbersome pre-treatments of samples and have the disadvantages of time consuming, large amount of reagents, high energy consumption, and high risk of environmental pollution, which are hard to satisfy the increasing requirements of rapid detection. Although the emerging biosensor technology has the advantages of fast reaction speed and low detection limit, it cannot cope with the presence of multiple ions, and its application of practical samples still needs a further exploration. At present, the rapid analysis of metal ions can also be achieved by using organic mass spectrometry. Based on some previous researches, a method of internal extractive electrospray ionization mass spectrometry (iEESI-MS) was developed for rapid determination of lead in drinking water in this study. Firstly, a drop of 50 μL water sample was dropped onto the polytetrafluoroethylene filter membrane and then sent into an oven at 100 ℃ for 15 min until the water completely evaporated. o-Phenanthroline (Phen) solution was selected as a complexing agent to extract lead on the dry filter membrane, and the Phen-Pb complexes were analyzed in real time by mass spectrometer. The results indicated that the concentration of Pb²⁺ can be detected as low as 1 μg/L. Meanwhile, the calibration curve had a good linear relationship between the intensity of mass spectrum peaks and the concentration of Pb2+ in the range of 1500 μg/L with the correlation coefficient (R²) of 99.4%, and the recovery was 117%. This fully demonstrates that the method has the advantages of fast detection, high sensitivity and good accuracy. Following this example, other metal ions in water can be further analyzed. In addition, when signals of Phen-Pb complexes were obtained, the signals of anions (such as NO^2-, Cl^-, SO₄^2-) and organic components in the mass spectrum could also be observed synchronously, showing the outstanding advantage of high throughput. In a word, this method has great potential to be used for implementing the simultaneous detection of multiple indicators in water.