As a chemical analysis technology,mass spectrometry has the advantages such as high specificity,high sensitivity and high quantitation accuracy,in comparison with other analysis methods.Mass spectrometry has a great application potential in the area of public security which is featured with needs of rapid on site detection on dangerous chemicals such as drugs,poisons and explosives.The analysis results also need to be quite accurate due to the potential significant impact on public lives following with the corresponding actions.While the specificity and the speed of mass spectrometry in analytical labs could meet the application needs for public security,some substantial development is still required to make the mass spectrometry analysis system suitable for rapid on-site detection.First of all,the instrument itself needs to become portable.Secondly,the sample preparation process needs to be simplified,so that everyone could perform the entire analysis process.Besides,the analysis results should be reported in a fashion directly supporting the decision making.A significant effort has been put into the miniaturization of mass spectrometers,and ambient ionization techniques have also been developed to replace traditional sample preparation.The target analytes in complex sample matrices could be directly analyzed by mass spectrometers without complicated sample treatment or chromatographic separation.In this review, we first introduce the development of ambient ionization techniques and their applications in the field of public security, along with details of several typical ambient ionization techniques(desorption electrospray ionization, direct analysis in real time, laser ablation electrospray ionization, paper spray ionization and paper capillary spray) such as their mechanisms, specifications and applications in public security.On site quantitation methods are also discussed here.Next,the development of integrated miniature mass spectrometry systems is reviewed.Through the two decade development,ambient ionization miniature mass spectrometer has evolved from the initial miniature ion traps to the miniature mass spectrometer that is only compatible with volatile chemicals,then to the miniature mass spectrometer that could analyze non volatile chemicals with traditional atmospheric ionization techniques and finally to the miniature mass spectrometer with ambient ionization source.Then,the applications of ambient ionization miniature mass spectrometer are demonstrated,including on site analysis of drugs of abuse and people with drug addiction,forensic analysis of explosives,agrochemical analysis that is related to food safety,and quality inspection of medicine.Finally,the future of ambient ionization miniature mass spectrometer is also speculated.It is a general trend for miniature mass spectrometer to be used together with ambient ionization.Wider applications of the ambient ionization miniature mass spectrometer could be achieved as it combines with cloud data platform in the future and becomes more intelligent.