Abstract: Electrospinning nanofiber exhibits several advantages, such as adjustable fiber diameter and distribution, interconnected pore structure, high porosity, high specific surface area, and controllable fiber packing density, which is a prominent research hot spot in recent years. Flame-retardant is an important characteristic of polymer materials, and flame-retardant fibers have the characteristic of higher safety in use compared to ordinary fibers. The development of nanofibers with flame-retardant properties is of great significance. Electrospinning technology refers to the jet spinning of polymer solutions or melts under strong electric fields, providing technical support for constructing nanofibers with special functions. It not only provides the possibility of combining functional fillers into polymers, but also provides the possibility of uniform dispersion of functional fillers within the polymer, which helps to more conveniently produce nanocomposites with special properties in situ. Based on this, this review introduced the development of flame-retardant nanofibers via electrospinning technology. Specially, the structure of electrospinning flame-retardant nanofibers was discussed, mainly including blend structure, core-shell structure, side-by-side structure, and porous structure. Their advantages and disadvantages were also emphasized. Moreover, the application status of flame-retardant nanofibers in lithium-ion battery separators, air filtration systems, fire alarm sensors, and protective materials were introduced. Finally, the future development directions of electrospinning flame-retardant nanofibers were foreseen.