The micro-nano fiber prepared by the high-temperature stretching method has the lowest optical transmission loss among all known sub-wavelength-scale optical waveguides due to its atomic surface smoothness and excellent material and geometric uniformity. At the same time, because vacuum or air is usually used as the cladding, it has a high core-cladding refractive index difference. The micro-nano fiber has strong optical field confinement, large-scale evanescent wave transmission, large-scale adjustable dispersion, and standard The compatibility of optical fiber and other series of characteristics give it unique advantages and potential application prospects in micro-nano-scale optical near-field coupling, light-material interaction, optical sensing, lasers, atomic optics, nonlinear optics, etc. The report first briefly introduces the basic optical properties of micro-nano fiber and its preparation and functionalization technology, and then introduces its main progress in near-field coupling, fiber sensing, fiber mode-locked laser and all-optical modulation, and related domestic and foreign related The research group's representative research work in atomic optics, nonlinear optics, optical mechanics, etc. Finally, briefly discuss the main challenges facing this direction, possible solutions and future development directions.