Abstract: As a precision measurement technology based on the principle of quantum mechanics, quantum metrology is becoming an important driving force for the development of various disciplines. The so-called single-spin quantum metrology here has two connotations. One is to use nitrogen-vacancy (NV) center, a kind of point defect in diamond, as single spin quantum information carrier, which could be accessed by optically detected magnetic resonance (MR). The other aspect refers to utilizing NV center as a single-spin quantum sensor through the manipulation of microwave/radio frequency, achieving microscopic MR with high sensitivity and high spatial resolution, and even reaching the level of single electron/nuclear spin detection. This technology replaces the traditional coil detection with quantum sensing, pushing MR study from macroscale to nanoscale, and the sample requirement from billions to single molecule level. Quantum metrology based on NV center is still in the stage of rapid growth. It has been applied in the research of two-dimensional material magnetism, superconductivity, single molecular structure and single cell magnetic detection. It is expected to provide significant support for the development of physics, chemistry, life science and even medicine. In this review, the basic concept and principle of single spin quantum metrology were introduced, and then the recent experimental progress of our group was elaborated on

Key words: quantum metrology, nitrogen-vacancy center, quantum sensor, single spin, microscopic magnetic resonance