Abstract: The heterogeneity between individual cells is essential for the realization of various biological functions. Accurate measurement of biomolecules at the single-cell scale is beneficial to obtain microcosmic biological mechanisms that are scarcely acquired at the tissue scale. However, the measurement of biomolecules in single cells is extremely difficult due to the complex composition in individual cells, the extremely low content of substances, and the significant differences in concentration of different components. With its high sensitivity, high specificity, accurate quantitation, and structural identification capabilities, mass spectrometry technology has attracted much attention in single-cell analysis field in recent years. At present, research on single-cell mass spectrometry methods has focused on the development of ionization techniques and corresponding sample pre-treatment methods. From the perspectives of ionization techniques, there are mainly four categories: nano-electrospray ionization mass spectrometry (nanoESI-MS), laser desorption ionization mass spectrometry (LDI-MS), secondary ion mass spectrometry (SIMS) and inductively coupled plasma mass spectrometry (ICP-MS). This review summarizes the recent developments of these methods and their future trends in metrology field.