The nano-scale imaging of magnetism is important for studying the microscopic local properties of matter. Nitrogen-vacancy (NV) scanning microscopy is such a technique based on NV center quantum sensing in diamond. As a magnetic imaging technique with a broad spectrum (DC to GHz), high sensitivity (nT/Hz1/2
) and high spatial resolution (~10 nm，theoretical limit ~nm), it is able to image ferromagnetic material, electric current distribution, electric conductivity, and even the spin of a single electron and a few nuclear spins on the nano-scale. This review introduces the principle of NV quantum sensing and magnetic imaging based on its microstructure and properties. The structure of a NV scanning microscope, fabrication of NV probes, and methods to determine their main parameters are then described. Finally, we select some representative published works on the application of NV scanning microscopy in different fields.