Electrospinning (E-spinning) is a versatile and effective method for the preparation of nanofibers with advantages of fiber continuity, large specific surface area, and wide material sources. This chapter discusses electrospun (E-spun) nanofibers can be used as cell scaffolds for drug release or for trauma repair, and the applications. It summarises the interesting applications of E-spun fibers in fuel cell electrode catalytic carriers, photocatalysts, biosensor catalysts, and gas sensor catalytic carriers. Multilevel structured air filter membranes with nanostructures on E-spun nanofibers can also improve the filtration performance. E-spun nanofibers can not only effectively filter out the particulate matter in the water by physical action, but can also kill the harmful bacteria in the water body by biochemical action after the surface modification in order to further improve the purification effect of drinking water. Bjorge et al. deposited silver nanoparticles on polyacrylic acid E-spun nanofibers and then used them to filter and kill bacteria during drinking water filtration.