Abstract: Microplastics are high molecular-weight polymers with micro- or nano-meter size, which have become a major global environmental issue in recent decades due to their ubiquity in the environment, bioavailability and potential toxicity. New analytical methods for the characterization of microplastics and nanoplastics are quickly emerging, such as particle size measurement, component identification and quantification. Many techniques have been developed and applied for the characterization of microplastics, such as Fourier-transform infrared spectroscopy, Raman spectroscopy and mass spectrometry (MS), etc. In recent years, the continuous development of MS technology has drawn more and more attention to the characterization and the environmental impact of microplastics. This paper mainly reviewed the state-of-the-art development and application of MS in microplastics analysis during the past decade. The principles and characteristics of various MS techniques used in the qualitative and quantitative analysis of microplastics were described, including thermal analysis coupled with MS-based techniques, elemental analytical MS, MALDI-ToF MS, LC-MS and ToF-SIMS. MS can provide chemical structure, molecular weight, degree of polymerization, additives, main functional groups and other information about the polymers, so it can be widely applied for chemical characterization, particle size determination and semi-quantitative/quantitative analysis of microplastics of small size. It has the advantages of replicable, fast real-time in situ analysis and high throughput detection, which can not only detect microplastics in the environment but also in biological tissues or cells in situ, showing great application potential in the research on the source, migration, transformation and interaction with biological organisms. The microplastics have been detected in the ocean, atmosphere, soil, consumer products, organisms and even human tissue, including polyethylene, polyamide, polyvinyl chloride, polypropylene, polystyrene, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, etc. The health risks of ingestion of microplastics deserve further exploration, especially nano plastics. The continuous development of MS technique and its combination with other separation/characterization methods will greatly promote the analysis of microplastics, and MS will become a more and more powerful tool in this research field and provide important scientific basis for the control of microplastic pollution.