Abstract: Water-soluble ions are the main components of atmospheric particulate matter, and play a key role in the source appointment of particulate matters. This paper reviews offline and online monitoring methods, instruments and measurement standards for water-soluble ions in atmospheric particulate matter, analyzes the current status of offline and online monitoring measurement technologies and protocols, and presents the problems such as the lack of reference materials in the pre-treatment of filter membrane samples in offline monitoring, and the large number of gaps in measurement methods, reference materials and standard devices in online monitoring. In view of the above problems, the development direction of metrology research is prospected.